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.
The grammar now allows for leading underscores for variable names. This
addresses a problem stemming from the fact that the imjournal module
will create variables using the given name from systemd. All "trusted"
variables in systemd begin with a leading underscore.
