Also now permit interactivly running tests without explicitly setting
$srcdir. This now works if we are inside ./tests and fails, as before,
when we are in a different directory.
Detected by shellcheck via CodeFactor.io
changes some of the test commands to use bash functions
includes some small bug fixes to tests where bugs were
previously not seen due to different plumbing.
Also a couple of changes to testbench worth mentioning:
* use cp -f to ensure files can be overwirtten in VBUILD
* fix issue of missing include test file in EXTRA_DIST
* new supressions
* testbench: try to use local system dependency cache
avoid going to Internet repos if not absolutely necessary. For
development containers, they should be pre-populated with the
important dependencies.
* do not enable libfaketime if ASAN is selected
unfortunately, libfaketime does not work in that case
see also https://github.com/rsyslog/rsyslog/issues/174
