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
A change in the inode was not detected under all circumstances,
most importantly not in some logrotate cases.
Includes new tests made by Andre Lorbach. They now use the
logrotate tool natively to reproduce the issue.
