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
- DEAD_PORT now uses unassigned IANA port unlike to be used on the system
(dynamic port querying is racy and we had at least once an issue, so we
can remove ambiguity here easily)
- replace some diag.sh commands by bash functions
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.
