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.
We cannot rely that libfaketime will be in system's LD search path. Also we do not
know libfaketime's SONAME (can be changed in future).
This patch will use "find" to determine latest libfaketime.so in "/usr".
Fixes: https://github.com/rsyslog/rsyslog/issues/992