Also remove old golang 1.13 version

This Go release is EOL now.

Don't drop support for Go1.12 and Go1.13 yet. Even though those Go releases are
also EOL since long ago, they are still being used inside SlapOS:

Go1.12 - by gitlab  (/cc @jerome, @alain.takoudjou)
Go1.13 - by galène  (/cc @tomo, @alain.takoudjou)

Component should not change a global setting like Go/Python/GCC version.
Only leaf software-releases can.

Going Go1.15.8 -> Go1.15.10 brings in fixes to compiler, runtime and stdlib
including security fixes to archive/zip and encoding/xml:

https://golang.org/doc/devel/release.html#go1.15.minor

Tested on helloworld SR (by adjusting it to use go1.15 instead of go1.16).

Going Go1.16 -> Go1.16.2 brings in fixes to compiler, runtime and stdlib
including security fixes to archive/zip and encoding/xml:

https://golang.org/doc/devel/release.html#go1.16.minor

Tested on helloworld SR.

See merge request !938

Before this commit, running
  'slapos node software'
and
  'supervisorctl start slapos-node-software'
behaved differently because the PATH and other environment variables
where different in the interactive theia shell and in supervisord.

Add a test to check that the PATH is the same for the interactive shell
and the supervisord services. This is important because slapos commands
like 'slapos node software' may behave differently in the shell and the
as supervisord services otherwise - each undoing what the other builds.

SlapOS Master is going to use Wendelin.core 2.
Wendelin.core 2 works with either ZODB4-wc2, or ZODB5, but not with ZODB4(*).
ERP5 does not currently work with ZODB5.
-> this leaves ZODB4-wc2 as the only choice.

(*) see nexedi/ZODB@8e7eab33
for details.

/reviewed-by @tomo, @rafael
/reviewed-on nexedi/slapos!944

See merge request nexedi/slapos!937

If key or csr are already present, we should not re-run this
openssl command which generates a new key and a new CSR.

hashlib.md5 needs bytes, read the file as binary to prevent

    TypeError: Unicode-objects must be encoded before hashing

slapos-testing, slapos-sr-testing: Don't duplicate instance.cfg prologue that is already provided by stack/nxdtest/instance.cfg

This software releases switched to nxdtest in 1536ad2e (software/slapos-testing: use nxdtest)
and 3a1e5628 (software/slapos-sr-testing: use nxdtest). So there is no
longer need to duplicate that standard instance prologue that is
provided by stack/nxdtest/instance.cfg:

https://lab.nexedi.com/nexedi/slapos/blob/0803b816/stack/nxdtest/instance.cfg.in#L1-8

/reviewed-by @jerome
/reviewed-on !94

On older kernels (like default one in Debian 9) firewalld is failing with:

'python-nftables' failed: internal:0:0-0: Error: Could not process rule: No such file or directory

when nftables backend is used.

As firewald component shall be compatibility layer, it shall work on most
different operating system, and for today it seems the way to make it really
compatible.

Missing exec results with receiving signals to the wrapper itself, leaving
the child process escaping signal control.

See previous commit.

This may lead to weird like ...//... or worse: here, the [gcc] part of
the tested SR will do "os.path.dirname('/usr/bin/')" (when using system
gcc), causing ${gcc:prefix} to be invalid ('/usr/bin' instead of '/usr')
and most sharable parts will rebuild (different [gcc] signature).

See c170fe3e and ZODB@8e7eab33
where ZODB4-wc2 is introduced.

See c170fe3e and nexedi/ZODB@8e7eab33
where ZODB4-wc2 is introduced.