Cleanup of locks

[dgoetz]

It would be create if dlm could clean up its data.

On the one side we have the locks itself which get autocreated but never cleaned up. It would be good to have a setting to delete them after a fixed time if the lock was not used (updated_at) and is not acquired (host_id). If you are willing for an even more complex logic it could query if no host exists any longer which had acquired the lock in the past.

On the other side is the history for the lock which also grows infinitely which should be limited by time and / or number of entries.