We have to append ">>" to /etc/mailman.cfg and not to overwrite previously written content with ">".
Problem was that the database config made in setup_database was overriden.
* Add code for auto-detecting database class for common cases.
* Fix unintentional space indentation instead of proper tab indentation
* Fix another left-over spaces indentation (sorry)
Even though the 'master.lck' is supposed to prevent race conditions, it needs to
be manually removed if the container did not shutdown gracefully. Remove the
manual check for the lock file and force mailman to remove it.
Also, set the stop_grace_period to 30s, which would allow Core to stop
gracefully and not leave the lock file over. Default value in case of Docker is 10s.
