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.
This provides a new-style alternative to $AbortOnUncleanConfig.
Note that a testbench test was changed to the new syntax. Adding
an additional test did not look useful, as the testbench still
sufficiently tests old and new method.
closes https://github.com/rsyslog/rsyslog/issues/2744
