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
Support tools (like tcpflood) are also upgraded to support the
necessary dynamic port.s
This is part of the effort to make parallel testing possible.
We move parts of the cleanup to the buildbot cleanup, as we cannot
clean out instances on each test when we run parallel tests.
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.
and do not fail just because journalctl is missing on the system.
The latter e.g. is the case for example on Ubuntu 14.04, which has
journal support inside the OS, but no journalctl.
