Authmode and peer settings were set afer new TLS Session initialized.
This caused all sessions to be handeled with certvalid mode instead
of the configired authmode.
Changed verify_callback to only log certificate errors into debug
log now when anon authmode is configured.
Fixed sndrcv ossl tests by using mixed certificates now.
closes: https://github.com/rsyslog/rsyslog/issues/3037
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
