Set expiry time to locks, just in case for some reason they get stuck.
Set default locks expiry time to 12 hours
If found lock is for a ready job, ignore it.

ready - revoked, finished or failed.
Add cleanup_tasks job.

Enumerates all locks and removes those of non existing jobs. Useful
for case the worker is being cold restarted, and jobs are finished
properly.
Use correct logging level
Merge pull request #281 from EverythingMe/fix_stuck_jobs

Several fixes to reduce cases of stuck jobs