The second line of changes related to replacing xtrabackup with
mariabackup:

1) All unnecessary references to xtrabackup are removed from
the documentation, from some comments, from the control files
that are used to prepare the packages.

2) Made corrections of the tests from the galera_3nodes suite
that mentioned xtrabackup or the old (associated with xtrabackup)
version of innobackupex.

3) Fixed flaws in the galera_3nodes mtr suite control scripts,
because of which they could not work with mariabackup.

4) Fixed numerous bugs in the SST scripts and in the mtr test
files (galera_3nodes mtr suite) that prevented the use of Galera
with IPv6 addresses.

5) Fixed flaws in tests for rsync and mysqldump (for galera_3nodes
mtr tests suite). These tests were not performed successfully without
these fixes.

https://jira.mariadb.org/browse/MDEV-17835

Now that InnoDB startup drops tables whose name starts with #sql,
the table ID alone should be enough to create a unique table name.

dict_temp_file_num, dict_mem_init(): Remove.

dict_mem_create_temporary_tablename(): Use a combination of
"#sql-ib" and the ID of the table that is being rebuilt
in TRUNCATE TABLE, or discarded in the commit of table-rebuilding
ALTER TABLE...ALGORITHM=INPLACE, or deferred to the DROP queue.

Thanks to Sergey Vojtovich for pointing this out.

fix the AWS SDK build eligibility checks.

followup for 779151db

MDEV-18064: Packaging is broken for debian-based systems

Packaging is broken for debian-based systems after removing
xtrabackup scripts. This is due to the fact that links to the
scripts are not removed from the installation file
(from the debian/mariadb-server-10.3.install).

Also in this fix some comments have been added to the
documentation, indicating that using xtrabackup[-v2] is
an deprecated, therefore user should use mariabackup instead.

https://jira.mariadb.org/browse/MDEV-18064

Add check for git command and test for internet connectivity
using bash /dev/tcp interface, instead of wget and curl which might
not be available, thus reducing dependencies for this script.

Reising condition on NOTW controlled by OPTION_SQL_NOTES.

DEV-17835: Remove wsrep-sst-method=xtrabackup

Starting with commit 6b698715
the encrypted page checksum is only computed with crc32.
Encrypted data pages that were written earlier can contain
other checksums, but new ones will only contain crc32.

Because of this, it does not make sense to implement strict
checks of innodb_checksum_algorithm for other than strict_crc32.

fil_space_verify_crypt_checksum(): Treat strict_innodb as innodb
and strict_none as none. That is, allow a match from any of the
algorithms none, innodb, crc32. (This is how it worked before the
second MDEV-12112 fix.)

Thanks to Thirunarayanan Balathandayuthapani for pointing this out.

DEV-17786: Add mariabackup test case for galera_sst_xtrabackup-v2_data_dir

fil_space_verify_crypt_checksum(): Compute the bug-compatible variant
of the CRC-32C checksum if the correct one does not match.

fil_space_verify_crypt_checksum(): Add a dummy return statement
in case memory is corrupted and innodb_checksum_algorithm has
an invalid value.

The initial fix only covered a part of Mariabackup.
This fix hardens InnoDB and XtraDB in a similar way, in order
to reduce the probability of mistaking a corrupted encrypted page
for a valid unencrypted one.

This is based on work by Thirunarayanan Balathandayuthapani.

fil_space_verify_crypt_checksum(): Assert that key_version!=0.
Let the callers guarantee that. Now that we have this assertion,
we also know that buf_page_is_zeroes() cannot hold.
Also, remove all diagnostic output and related parameters,
and let the relevant callers emit such messages.
Last but not least, validate the post-encryption checksum
according to the innodb_checksum_algorithm (only accepting
one checksum for the strict variants), and no longer
try to validate the page as if it was unencrypted.

buf_page_is_zeroes(): Move to the compilation unit of the only callers,
and declare static.

xb_fil_cur_read(), buf_page_check_corrupt(): Add a condition before
calling fil_space_verify_crypt_checksum(). This is a non-functional
change.

buf_dblwr_process(): Validate the page only as encrypted or unencrypted,
but not both.

MDEV-17848: Galera test failure on galera_sst_xtrabackup-v2[_data_dir]

A static analysis tool suggested that in the function
row_merge_read_clustered_index(), ut_free(nonnull) could
be invoked twice for nonnull!=NULL. While a manual review
of the code disproved this, it should not hurt to clean up
the code so that the static analysis tool will not complain.

index_tuple_info_t::insert(), row_mtuple_cmp(): Remove the
parameter mtr_committed, which duplicated !mtr->is_active().

row_merge_read_clustered_index(): Initialize row_heap = NULL.
Remove a duplicated call mem_heap_empty(row_heap) that was
inadvertently added in commit cb1e76e4.

Replace a "goto func_exit" with "break", to get consistent error
handling for both failures to create or write a temporary file.

end_of_index: Assign row_heap=NULL and nonnull=NULL to prevent
double freeing.

func_exit: Check for row_heap!=NULL before invoking mem_heap_free().

Closes #959

The use of the xtrabackup and xtrabackup-v2 methods for SST
has been declared obsolete since version 10.2, now it cannot
be used because of the different redo log format. Accordingly,
we need to remove the xtrabackup-related scripts and dynamically
replace the call to xtrabackup[-v2] to the mariabackup (with a
corresponding warning in the log) when the server performs SST.

https://jira.mariadb.org/browse/MDEV-17835

Remove provider defaults check from 'galera_defaults' MTR test

Problem is that if you use bundled yassl AES_CTR is not supported. There is a way to detect that but as we really want to keep this test enabled did not add
skip for missing support. Changed method to AES_CBC as there is no need to
use AES_CTR.

Add check that file key management plugin is found.

While calculating distinct with the function remove_dup_with_compare, we don't have rnd_end calls
when we have completed the scan over the temporary table.
Added ha_rnd_end calls when we are done with the scan of the table.

galera_prepared_statement test fixed.

connect.xml2 test result fixed.

The error message modified.
Then the TABLE_SHARE::error_table_name() implementation taken from 10.3,
          to be used as a name of the table in this message.

ported privilege checking from xtrabackup.
Now, mariabackup would terminate early if either RELOAD or PROCESS privilege
is not held, not at the very end of backup

The behavior can be disabled with nre setting --check-privileges=0.
Also , --no-lock does not need all of these privileges, since it skips
FTWRL and SHOW ENGINE STATUS INNODB.

From time to time Galera adds new parameters or changes defaults to
existing ones. Every time this happens galera_defaults test needs a
fix (and a commit) because it insists on checking these defaults.
This is making life hard because any Galera update may require a fix
to MariaDB code even though it is totally unrelated and defeats the
whole idea of a provider living its own life.
This commit removes checking for provider defaults to avoid false
positive failures on MariaDB side.

Internal transactions may not have trx->mysql_thd.
But at the same time, trx->duplicates should only hold if
REPLACE or INSERT...ON DUPLICATE KEY UPDATE was executed from SQL.

The flag feels misplaced. A more appropriate place for it would
be row_prebuilt_t or similar.

After validating the post-encryption checksum on an encrypted page,
Mariabackup should decrypt the page and validate the pre-encryption
checksum as well. This should reduce the probability of accepting
invalid pages as valid ones.

This is a backport and refactoring of a patch that was
originally written by Thirunarayanan Balathandayuthapani
for the 10.2 branch.

Innochecksum was being built as if WITH_INNODB_BUG_ENDIAN_CRC32:BOOL=OFF
had been specified.

Also, clean up tests:

innodb.innochecksum: Useless; superceded by innodb_zip.innochecksum.
innodb.innodb_zip_innochecksum: Remove; duplicated innodb_zip.innochecksum.
innodb.innodb_zip_innochecksum2: Remove; duplicated innodb_zip.innochecksum_2.
innodb.innodb_zip_innochecksum3: Remove; duplicated innodb_zip.innochecksum_3.

No test case was added. I tested manually by adding debug instrumentation
to both innochecksum and buf_page_is_checksum_valid_crc32() to make
innochecksum write the buggy crc32, and to get warnings for falling back
to the buggy checksum. Automating this would require that tests be
adjusted depending on the build options.

Allow array binding for DELETE, test it.