In commit 5f13cc85 I changed enum encodings from int32 to int8, but did
not noticed that NEO/py commit 52db5607 ("protocol: a single byte is
more than enough to encode enums") despite specified intent and
ErrorCodes being marked with @Enum, changed encoding only for fields
that are marked as PEnum in structures. In NEO/py the Error.code field
is still marked as PNumber which encodes as 32-bit integer on the wire.
-> Fix it back.

With recent xtesting.DrvTestLoad update this error was manifesting itself as (on @t branch):

--- FAIL: TestLoad (2.08s)
    --- FAIL: TestLoad/py (2.07s)
        xtesting.go:306: load 0285cbac258bf265:0000000000000000: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 0285cbac258bf265:0000000000000000: 127.0.0.1:42288 - 127.0.0.1:37109 .5: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 0285cbac258bf265:0000000000000000: 0000000000000000: object was not yet created
        xtesting.go:306: load 0285cbac3d0369e5:0000000000000001: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 0285cbac3d0369e5:0000000000000001: 127.0.0.1:42288 - 127.0.0.1:37109 .13: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 0285cbac3d0369e5:0000000000000001: 0000000000000001: object was not yet created
        xtesting.go:306: load 0285cbac41b4e832:0000000000000002: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 0285cbac41b4e832:0000000000000002: 127.0.0.1:42288 - 127.0.0.1:37109 .21: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 0285cbac41b4e832:0000000000000002: 0000000000000002: object was not yet created
        xtesting.go:306: load 0285cbac4666667f:0000000000000003: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 0285cbac4666667f:0000000000000003: 127.0.0.1:42288 - 127.0.0.1:37109 .29: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 0285cbac4666667f:0000000000000003: 0000000000000003: object was not yet created
        xtesting.go:306: load 0285cbac4fc96318:0000000000000004: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 0285cbac4fc96318:0000000000000004: 127.0.0.1:42288 - 127.0.0.1:37109 .41: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 0285cbac4fc96318:0000000000000004: 0000000000000004: object was not yet created
        xtesting.go:306: load 0285cbac547ae165:0000000000000005: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 0285cbac547ae165:0000000000000005: 127.0.0.1:42288 - 127.0.0.1:37109 .49: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 0285cbac547ae165:0000000000000005: 0000000000000005: object was not yet created
        xtesting.go:306: load 0285cbac628f5c4b:0000000000000006: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 0285cbac628f5c4b:0000000000000006: 127.0.0.1:42288 - 127.0.0.1:37109 .65: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 0285cbac628f5c4b:0000000000000006: 0000000000000006: object was not yet created
        xtesting.go:306: load 0285cbaca444447f:0000000000000007: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 0285cbaca444447f:0000000000000007: 127.0.0.1:42288 - 127.0.0.1:37109 .125: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 0285cbaca444447f:0000000000000007: 0000000000000007: object was not yet created
        xtesting.go:306: load 0285cbacbbbbbbff:0000000000000008: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 0285cbacbbbbbbff:0000000000000008: 127.0.0.1:42288 - 127.0.0.1:37109 .149: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 0285cbacbbbbbbff:0000000000000008: 0000000000000008: object was not yet created
        xtesting.go:306: load 0285cbad80da7498:0000000000000009: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 0285cbad80da7498:0000000000000009: 127.0.0.1:42288 - 127.0.0.1:37109 .269: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 0285cbad80da7498:0000000000000009: 0000000000000009: object was not yet created
        xtesting.go:331: load 7fffffffffffffff:000000000000000a: returned err unexpected:
            have: neo://1@127.0.0.1:32731: load 7fffffffffffffff:000000000000000a: 127.0.0.1:42288 - 127.0.0.1:37109 .295: decode: decode: buffer overflow
            want: neo://1@127.0.0.1:32731: load 7fffffffffffffff:000000000000000a: 000000000000000a: no such object

Before this patch and with updated DrvTestLoad (see previous patch) it was failing as:

--- FAIL: TestLoad (0.52s)
    --- FAIL: TestLoad/py/msgpack=false (0.25s)
        xtesting.go:306: load 0285cbac258bf265:0000000000000000: returned err unexpected:
            have: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac258bf265:0000000000000000: /tmp/zeo535364855/1.fs.zeosock: call loadBefore: unexpected reply: got ogórek.None{}; expect 3-tuple
            want: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac258bf265:0000000000000000: 0000000000000000: no such object
        xtesting.go:306: load 0285cbac3d0369e5:0000000000000001: returned err unexpected:
            have: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac3d0369e5:0000000000000001: /tmp/zeo535364855/1.fs.zeosock: call loadBefore: unexpected reply: got ogórek.None{}; expect 3-tuple
            want: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac3d0369e5:0000000000000001: 0000000000000001: no such object
        xtesting.go:306: load 0285cbac41b4e832:0000000000000002: returned err unexpected:
            have: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac41b4e832:0000000000000002: /tmp/zeo535364855/1.fs.zeosock: call loadBefore: unexpected reply: got ogórek.None{}; expect 3-tuple
            want: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac41b4e832:0000000000000002: 0000000000000002: no such object
        xtesting.go:306: load 0285cbac4666667f:0000000000000003: returned err unexpected:
            have: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac4666667f:0000000000000003: /tmp/zeo535364855/1.fs.zeosock: call loadBefore: unexpected reply: got ogórek.None{}; expect 3-tuple
            want: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac4666667f:0000000000000003: 0000000000000003: no such object
        xtesting.go:306: load 0285cbac4fc96318:0000000000000004: returned err unexpected:
            have: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac4fc96318:0000000000000004: /tmp/zeo535364855/1.fs.zeosock: call loadBefore: unexpected reply: got ogórek.None{}; expect 3-tuple
            want: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac4fc96318:0000000000000004: 0000000000000004: no such object
        xtesting.go:306: load 0285cbac547ae165:0000000000000005: returned err unexpected:
            have: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac547ae165:0000000000000005: /tmp/zeo535364855/1.fs.zeosock: call loadBefore: unexpected reply: got ogórek.None{}; expect 3-tuple
            want: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac547ae165:0000000000000005: 0000000000000005: no such object
        xtesting.go:306: load 0285cbac628f5c4b:0000000000000006: returned err unexpected:
            have: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac628f5c4b:0000000000000006: /tmp/zeo535364855/1.fs.zeosock: call loadBefore: unexpected reply: got ogórek.None{}; expect 3-tuple
            want: /tmp/zeo535364855/1.fs.zeosock: load 0285cbac628f5c4b:0000000000000006: 0000000000000006: no such object
        xtesting.go:306: load 0285cbaca444447f:0000000000000007: returned err unexpected:
            have: /tmp/zeo535364855/1.fs.zeosock: load 0285cbaca444447f:0000000000000007: /tmp/zeo535364855/1.fs.zeosock: call loadBefore: unexpected reply: got ogórek.None{}; expect 3-tuple
            want: /tmp/zeo535364855/1.fs.zeosock: load 0285cbaca444447f:0000000000000007: 0000000000000007: no such object
        xtesting.go:306: load 0285cbacbbbbbbff:0000000000000008: returned err unexpected:
            have: /tmp/zeo535364855/1.fs.zeosock: load 0285cbacbbbbbbff:0000000000000008: /tmp/zeo535364855/1.fs.zeosock: call loadBefore: unexpected reply: got ogórek.None{}; expect 3-tuple
            want: /tmp/zeo535364855/1.fs.zeosock: load 0285cbacbbbbbbff:0000000000000008: 0000000000000008: no such object
        xtesting.go:306: load 0285cbad80da7498:0000000000000009: returned err unexpected:
            have: /tmp/zeo535364855/1.fs.zeosock: load 0285cbad80da7498:0000000000000009: /tmp/zeo535364855/1.fs.zeosock: call loadBefore: unexpected reply: got ogórek.None{}; expect 3-tuple
            want: /tmp/zeo535364855/1.fs.zeosock: load 0285cbad80da7498:0000000000000009: 0000000000000009: no such object
    --- FAIL: TestLoad/py/msgpack=true (0.26s)
        xtesting.go:306: load 0285cbac258bf265:0000000000000000: returned err unexpected:
            have: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac258bf265:0000000000000000: /tmp/zeo794664426/1.fs.zeosock: call loadBefore: zlink is closed
            want: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac258bf265:0000000000000000: 0000000000000000: no such object
        xtesting.go:306: load 0285cbac3d0369e5:0000000000000001: returned err unexpected:
            have: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac3d0369e5:0000000000000001: /tmp/zeo794664426/1.fs.zeosock: call loadBefore: zlink is closed
            want: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac3d0369e5:0000000000000001: 0000000000000001: no such object
        xtesting.go:306: load 0285cbac41b4e832:0000000000000002: returned err unexpected:
            have: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac41b4e832:0000000000000002: /tmp/zeo794664426/1.fs.zeosock: call loadBefore: zlink is closed
            want: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac41b4e832:0000000000000002: 0000000000000002: no such object
        xtesting.go:306: load 0285cbac4666667f:0000000000000003: returned err unexpected:
            have: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac4666667f:0000000000000003: /tmp/zeo794664426/1.fs.zeosock: call loadBefore: zlink is closed
            want: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac4666667f:0000000000000003: 0000000000000003: no such object
        xtesting.go:306: load 0285cbac4fc96318:0000000000000004: returned err unexpected:
            have: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac4fc96318:0000000000000004: /tmp/zeo794664426/1.fs.zeosock: call loadBefore: zlink is closed
            want: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac4fc96318:0000000000000004: 0000000000000004: no such object
        xtesting.go:306: load 0285cbac547ae165:0000000000000005: returned err unexpected:
            have: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac547ae165:0000000000000005: /tmp/zeo794664426/1.fs.zeosock: call loadBefore: zlink is closed
            want: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac547ae165:0000000000000005: 0000000000000005: no such object
        xtesting.go:306: load 0285cbac628f5c4b:0000000000000006: returned err unexpected:
            have: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac628f5c4b:0000000000000006: /tmp/zeo794664426/1.fs.zeosock: call loadBefore: zlink is closed
            want: /tmp/zeo794664426/1.fs.zeosock: load 0285cbac628f5c4b:0000000000000006: 0000000000000006: no such object
        xtesting.go:306: load 0285cbaca444447f:0000000000000007: returned err unexpected:
            have: /tmp/zeo794664426/1.fs.zeosock: load 0285cbaca444447f:0000000000000007: /tmp/zeo794664426/1.fs.zeosock: call loadBefore: zlink is closed
            want: /tmp/zeo794664426/1.fs.zeosock: load 0285cbaca444447f:0000000000000007: 0000000000000007: no such object
        xtesting.go:306: load 0285cbacbbbbbbff:0000000000000008: returned err unexpected:
            have: /tmp/zeo794664426/1.fs.zeosock: load 0285cbacbbbbbbff:0000000000000008: /tmp/zeo794664426/1.fs.zeosock: call loadBefore: zlink is closed
            want: /tmp/zeo794664426/1.fs.zeosock: load 0285cbacbbbbbbff:0000000000000008: 0000000000000008: no such object
        xtesting.go:306: load 0285cbad80da7498:0000000000000009: returned err unexpected:
            have: /tmp/zeo794664426/1.fs.zeosock: load 0285cbad80da7498:0000000000000009: /tmp/zeo794664426/1.fs.zeosock: call loadBefore: zlink is closed
            want: /tmp/zeo794664426/1.fs.zeosock: load 0285cbad80da7498:0000000000000009: 0000000000000009: no such object

This currently fails on ZEO and NEO. Those storages will be fixed in the
following patches (NEO only on @t branch for now).

Starting from Go1.10 `go test` caches successful test results[1].
However we want to torture the implementation and run the tests for real
each time `neotest test-go` is ran.

-> Disable tests caching

[1] https://golang.org/doc/go1.10#test

See:

- https://lab.nexedi.com/nexedi/nxdtest
- https://lab.nexedi.com/nexedi/nxdtest/blob/master/nxdtest/__init__.py
- nexedi/nxdtest@d575236a
- nexedi/slapos!839

-> Leave only .nxdtest file with neotest-specific bits to be run by
nxdtest driver.

* origin/old-proto:
  qa: skip broken ZODB test
  client: fix race with invalidations when starting a new transaction on ZODB 5
  Code clean-up, comment fixes
  master: fix crash in STARTING_BACKUP when connecting to an upstream secondary master
  mysql: workaround for MDEV-20693
  client: inline Application._loadFromCache
  client: replace global load lock by a per-oid one
  client: unindent code
  client: remove load lock in tpc_finish
  qa: check cache in testExternalInvalidation
  qa: comment testExternalInvalidation2

This protocol version corresponds to protocol version used by NEO/py
v1.12 and was set in NEO/py commit c6453626 (Bump protocol version).

The protocol definition was updated to match that NEO/py release in
the previous patches.

This corresponds to NEO/py commit 2a27239d (tweak: add option to
simulate).

This corresponds to NEO/py commit c2c9e99d (Better error reporting from
the master to neoctl for denied requests).

This corresponds to NEO/py commit 21190ee7 (Make 'neoctl print pt'
report the number of replicas).

This corresponds to NEO/py commit ef5fc508 (Make the number of replicas
modifiable when the cluster is running).

One important change in the protocol is that Client no longer queries
Master for partition table - instead M pushed partTab to C right after
identification (after pushing nodeTab).

See also: https://neo.nexedi.com/P-NEO-Protocol.Specification.2019?portal_skin=CI_slideshow#/9/5

This corresponds to NEO/py commit 27e3f620 (New --new-nid storage option
for fast cloning).

NEO 1.12

* tag 'v1.12': (28 commits)
  Release version 1.12
  master: reject drop/tweak ctl commands that could lead to unwanted status
  qa: extend test reproducing the migration of a big ZODB to NEO
  neoctl: better display of full partition tables
  Bump protocol version
  tweak: add option to simulate
  tweak: do not crash when trying to remove all nodes
  tweak: do not touch cells of nodes that are intended to be dropped
  Better error reporting from the master to neoctl for denied requests
  Make 'neoctl print pt' report the number of replicas
  Make the number of replicas modifiable when the cluster is running
  New --new-nid storage option for fast cloning
  qa: fix 2 tests with ZODB5
  qa: new tools/stress options to evaluate MySQL engines
  qa: provide a way to let tests start 1 mysqld per storage node
  mysql: make 'user' actually optional in the DB connection string
  mysql: specify column families for RocksDB
  qa: add testIncremental (testImporter) test
  importer: fix hidden "maximum recursion depth exceeded" at startup
  importer: fix closure of ZODB, and also do it when the import is finished
  sqlite: fix resumption of migration to NEO with Importer
  qa: fix a random failure in threaded tests
  importer: speed up startup when the import is already finished
  importer: fix replication (as source) once import is finished
  storage: fix DatabaseManager.getLastTID with max_tid
  qa: remove 2 useless unit tests
  storage: allow the master to change our node id
  Rename --uuid command-line options into --nid
  importer: fix possible data loss on writeback

This protocol version corresponds to protocol version used by NEO/py
v1.11 and was set in NEO/py commit 9a5b46dd (Bump protocol version).

The protocol definition was updated to match that NEO/py release in
the previous patch.

This corresponds to NEO/py commit 64826794 (New neoctl command to flush
the logs of all nodes in the cluster).

NEO 1.11

* tag 'v1.11': (52 commits)
  Release version 1.11
  Fix short descriptions of neoctl & neomigrate in their headers
  Update copyright year
  qa: new tool to stress-test NEO
  master: fix typo in comment
  Fix error handling when setting up a listening connector
  Fix incomplete/incorrect mapping of node ids in logs
  Fix log corruption on rotation in multi-threaded applications (e.g. client)
  sqlite: optimize storage of metadata
  neolog: do not die when a table is corrupted
  neolog: add support for zstd-compressed logs
  neolog: do not hardcode default value of -L option in help message
  fixup! New log format to show node id (and optionally cluster name) in node column
  New log format to show node id (and optionally cluster name) in node column
  fixup! client: discard late answers to lockless writes
  client: fix race condition between Storage.load() and invalidations
  client: fix race condition in refcounting dispatched answer packets
  More RTMIN+2 (log) information for clients and connections
  storage: check for conflicts when notifying that the a partition is replicated
  storage: clarify several assertions
  qa: new expectedFailure testcase method
  client: merge ConnectionPool inside Application
  client: prepare merge of ConnectionPool inside Application
  client: fix AssertionError when trying to reconnect too quickly after an error
  qa: fix attributeTracker
  storage: fix storage leak when an oid is stored several times within a transaction
  client: discard late answers to lockless writes
  qa: in threaded tests, log queued packets when "tic is looping forever"
  In logs, dump the partition table in a more compact and readable way
  storage: fix write-locking bug when a deadlock happens at the end of a replication
  client: log_flush most exceptions raised from Application to ZODB
  client: fix assertion failure in case of conflict + storage disconnection
  client: simplify connection management in transaction contexts
  client: also vote to nodes that only check serials
  qa: deindent code
  Bump protocol version
  client: fix undetected disconnections to storage nodes during commit
  Fix data corruption due to undetected conflicts after storage failures
  master: notify replicating nodes of aborted watched transactions
  New neoctl command to flush the logs of all nodes in the cluster
  storage: fix premature write-locking during rebase when replication ends
  client: fix race condition when a storage connection is closed just after identification
  storage: relax assertion
  comments, unused import
  storage: fix write-lock leak
  client: fix possible corruption in case of network failure with a storage
  qa: comment about potential freeze when a functional test ends
  storage: fix assertion failure in case of connection reset with a client node
  qa: document a rare random failure in testExport
  debug: add script to trace all accesses to the client cache
  Use argparse instead of optparse
  neolog: use argparse instead of optparse
  Add comment about dormant bug when sending a lot of data to a slow node
  client: make clearer that max_size attribute is used from outside ClientCache

This protocol version corresponds to protocol version used by NEO/py v1.10.

The protocol definition was updated to match that NEO/py release in
the previous patches.

This corresponds to NEO/py commit 97af23cc (Maximize resiliency by
taking into account the topology of storage nodes).

- Rename GetObject .Tid    -> .Before
- Rename GetObject .Serial -> .At
- Sync docstrings

This corresponds to NEO/py commit 9f0f2afe (protocol: update packet
docstrings).

This corresponds to NEO/py commit 52db5607 ("protocol: a single byte is
more than enough to encode enums").

Don't skip a code when going request1->request2 through `Request1
Answer1 Request2`. For example before this patch:

	1		RequestIdentification
	1 | answerBit	AcceptIdentification
	3		Ping
	3 | answerBit	Pong
	...

after this patch:

	1		RequestIdentification
	1 | answerBit	AcceptIdentification
	2		Ping
	2 | answerBit	Pong
	...

This corresponds to NEO/py commit a00ab78b ("protocol: small cleanup in
packet registration").

Corresponds to NEO/py commit b3dd6973 ("Optimize resumption of
replication by starting from a greater TID").

Corresponds to NEO/py commit 3efbbfe3 ("master: automatically discard
feeding cells that get out-of-date").

NEO 1.10

* tag 'v1.10': (55 commits)
  Release version 1.10
  Maximize resiliency by taking into account the topology of storage nodes
  storage: also commit updated cell TID at each replicated chunk of 'obj' records
  storage: skip useless work when unlocking transactions
  qa: flush logs at the end of each test when -L is not used
  qa: add a log in case that a mysterious bug happens again
  storage: clarify log about data deletion of discarded cells
  debug: new example to run the profiler for 1 minute
  mysql: fix replication of big oids (> 16M)
  tests/cluster: speedup waiting a bit
  protocol: update packet docstrings
  Bump protocol version
  protocol: a single byte is more than enough to encode enums
  protocol: small cleanup in packet registration
  Optimize resumption of replication by starting from a greater TID
  importer: update comment about a workaround for ZODB3
  Micro-optimization of p64/u64
  qa: add a log in testBackupNodeLost for easier debugging
  Document that the bug when checking replicas may also cause the master to crash
  storage: stop logging 'Abort TXN' for txn that have been locked
  storage: split _migrate2() for reusable _alterTable()
  qa: new testStorageUpgrade
  qa: update testStorageUpgrade data for what is not automatically upgraded
  qa: original data for the future testStorageUpgrade
  sqlite: fix indexes of upgraded db
  importer: fix NameError when recovering during tpc_finish
  fixup! importer: fetch and process the data to import in a separate process
  Serialize empty transaction extension with an empty string
  client: fix partial import from a source storage
  qa: give a title to subprocesses of functional tests
  importer: give a title to the 'import' and 'writeback' subprocesses
  importer: fetch and process the data to import in a separate process
  importer: new option to write back new transactions to the source database
  importer: log when the transaction index for FileStorage DB is built
  importer: open imported zodb in read-only whenever possible
  fixup! mysql: fix remaining places where a server disconnection was not catched
  fixup! storage: speed up replication by sending bigger network packets
  mysql: do not full-scan for duplicates of big oids if deduplication is disabled
  mysql: fix remaining places where a server disconnection was not catched
  fixup! Add support for custom compression levels
  importer: reenable compression by default
  qa: review testImporter
  qa: remove a few uses of 'chr'
  Fix a few issues with ZODB5
  importer: small code cleanup in speedupFileStorageTxnLookup patch
  importer: do not trigger speedupFileStorageTxnLookup uselessly
  Add support for custom compression levels
  setup: update MANIFEST.in
  importer: do not checksum data twice
  client: store uncompressed if compressed size is equal
  fixup! master: automatically discard feeding cells that get out-of-date
  master: automatically discard feeding cells that get out-of-date
  qa: remove useless indentation in testSafeTweak
  bench: new option to mesure ZEO perfs in matrix test
  bench: reduce number of partitions in matrix test
  storage: fix replication of creation undone

ZEO4 does not have msgpack support and does not take $ZEO_MSGPACK into
account. With ZEO4 this test was failing before:

	--- FAIL: TestHandshake (0.46s)
	    --- FAIL: TestHandshake/py/msgpack=true (0.24s)
	        zeo_test.go:241: handshake: encoding=Z  ; want M

We don't have infrastructure to check python packages versions, so
check it by verifying ZEO.asyncio presence.

In that case at0 was initialized as 0 and still considered uninitialized
by flushEventq0:

    (neo) (z-dev) (g.env) kirr@deco:~/src/neo/src/lab.nexedi.com/kirr/neo/go/zodb/storage/zeo$ go test -run Empty
    ------
    2020-10-12T07:39:25 INFO ZEO.runzeo (146240) opening storage '1' using FileStorage
    ------
    2020-10-12T07:39:25 INFO ZEO.StorageServer StorageServer created RW with storages: 1:RW:/tmp/zeo905263273/1.fs
    ------
    2020-10-12T07:39:25 INFO ZEO.asyncio.server listening on /tmp/zeo905263273/1.fs.zeosock
    ------
    2020-10-12T07:39:25 INFO ZEO.asyncio.base Connected server protocol
    ------
    2020-10-12T07:39:25 INFO ZEO.asyncio.server received handshake 'Z5'
    2020/10/12 07:39:25 /tmp/zeo905263273/1.fs.zeosock: EOF
    --- FAIL: TestEmptyDB (0.22s)
        --- FAIL: TestEmptyDB/py/msgpack=false (0.22s)
    panic: flush, but .at0 not yet initialized [recovered]
            panic: flush, but .at0 not yet initialized

    goroutine 7 [running]:
    testing.tRunner.func1.1(0x644a60, 0x6e1a50)
            /home/kirr/src/tools/go/go/src/testing/testing.go:1072 +0x30d
    testing.tRunner.func1(0xc000001e00)
            /home/kirr/src/tools/go/go/src/testing/testing.go:1075 +0x41a
    panic(0x644a60, 0x6e1a50)
            /home/kirr/src/tools/go/go/src/runtime/panic.go:969 +0x175
    lab.nexedi.com/kirr/neo/go/zodb/storage/zeo.(*zeo).flushEventq0(0xc00018a000)
            /home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/zodb/storage/zeo/zeo.go:180 +0xf3
    lab.nexedi.com/kirr/neo/go/zodb/storage/zeo.openByURL(0x6e9ca0, 0xc000016108, 0xc000138120, 0xc000153d98, 0x0, 0x0, 0x0, 0x0, 0x0)
            /home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/zodb/storage/zeo/zeo.go:488 +0x5ba
    lab.nexedi.com/kirr/neo/go/zodb/storage/zeo.zeoOpen(0xc000018740, 0x1e, 0xc000049d98, 0x0, 0x0, 0x0, 0x0)
            /home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/zodb/storage/zeo/zeo_test.go:285 +0x17b
    lab.nexedi.com/kirr/neo/go/zodb/storage/zeo.withZEO.func1(0xc000001e00, 0x6e9ea0, 0xc00005e6c0)
            /home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/zodb/storage/zeo/zeo_test.go:219 +0xd0
    lab.nexedi.com/kirr/neo/go/zodb/storage/zeo.withZEOSrv.func2.1(0xc0000185c0, 0x16)
            /home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/zodb/storage/zeo/zeo_test.go:205 +0xfb
    lab.nexedi.com/kirr/neo/go/zodb/storage/zeo.withZEOSrv.func1(0xc000001e00, 0xc00000e5a0)
            /home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/zodb/storage/zeo/zeo_test.go:185 +0x129
    lab.nexedi.com/kirr/neo/go/zodb/storage/zeo.withZEOSrv.func2(0xc000001e00)
            /home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/zodb/storage/zeo/zeo_test.go:197 +0x105
    testing.tRunner(0xc000001e00, 0xc00000e440)
            /home/kirr/src/tools/go/go/src/testing/testing.go:1123 +0xef
    created by testing.(*T).Run
            /home/kirr/src/tools/go/go/src/testing/testing.go:1168 +0x2b3
    exit status 2
    FAIL    lab.nexedi.com/kirr/neo/go/zodb/storage/zeo     0.227s

-> Fix it by using dedicated field marking whether .at0 was initialized or not yet.

For virtio NICs /sys/class/net/<NIC>/device lead to $pcidev/virtioX, not just $pcidev, e.g.:

	$ realpath /sys/class/net/ens3/device
	/sys/devices/pci0000:00/0000:00:03.0/virtio0

and we were extracting virtio0 instead of 0000:00:03.0 as PCI device identifier.

-> Fix it by recognizing and stripping /virtioX suffix.

For example under KVM it was failing as

    cpu:	Intel(R) Xeon(R) CPU E5-2678 v3 @ 2.50GHz
    cat: /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq: No such file or directory
      File "<string>", line 1
        print '%.2fGHz' % ( / 1E6)
                            ^
    SyntaxError: invalid syntax

    $ lscpu
    Architecture:        x86_64
    CPU op-mode(s):      32-bit, 64-bit
    Byte Order:          Little Endian
    Address sizes:       40 bits physical, 48 bits virtual
    CPU(s):              40
    On-line CPU(s) list: 0-39
    Thread(s) per core:  1
    Core(s) per socket:  1
    Socket(s):           40
    NUMA node(s):        1
    Vendor ID:           GenuineIntel
    CPU family:          6
    Model:               63
    Model name:          Intel(R) Xeon(R) CPU E5-2678 v3 @ 2.50GHz
    Stepping:            2
    CPU MHz:             2494.238
    BogoMIPS:            4988.47
    Virtualization:      VT-x
    Hypervisor vendor:   KVM
    Virtualization type: full
    L1d cache:           32K
    L1i cache:           32K
    L2 cache:            4096K
    L3 cache:            16384K
    NUMA node0 CPU(s):   0-39
    Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl xtopology cpuid tsc_known_freq pni pclmulqdq vmx ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm invpcid_single pti tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid xsaveopt arat

-> Fix it by checking whether cpufreq/cpuidle directories are available, and display "?" if they are not.

======================================================================
FAIL: check_tid_ordering_w_commit (neo.tests.zodb.testBasic.BasicTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "ZODB/tests/BasicStorage.py", line 397, in check_tid_ordering_w_commit
    self.assertEqual(results.pop('lastTransaction'), tids[1])
  File "neo/tests/__init__.py", line 301, in assertEqual
    return super(NeoTestBase, self).assertEqual(first, second, msg=msg)
failureException: '\x03\xd8\x85H\xbffp\xbb' != '\x03\xd8\x85H\xbfs\x0b\xdd'

(cherry picked from commit f4cb59d2)

This requires ZODB >= 5.6.0

(cherry picked from commit a7d101ec)

(cherry picked from commit 43029be2)

Starting from Go1.14 defer is no longer slow:
https://golang.org/doc/go1.14#runtime

Starting from Go1.14 defer is no longer slow:
https://golang.org/doc/go1.14#runtime

This turns zeo tests to pass.
The bug is reported upstream here: https://github.com/zopefoundation/ZODB/issues/318

If xres fails to convert to tuple, we should error about xres, not res
which is always tuple(nil).