If KiCad crashes or exits without deleting the lockfile, don't show the
warning message unless we are not the one who locked it or there are
other KiCad instances running locally.
This should catch 99% of the cases where the message is shown
incorrectly. There may be some corner cases where the lock file is
created on a network drive using two different machines with the same
name and same user but these cases should be (famous last words)
sufficiently rare as to not be observed in practice
(cherry picked from commit 7fe83993cf)
