Fixed a logging level
Further cleanup
Small fix
Fix a memory leak of celery
Addressed all comments in https://github.com/gem/oq-engine/pull/1390
Merge pull request #1395 from gem/celery-memory-leak

Fix a memory leak of celery
Renamed collector->source_collector
Merge branch 'master' of github.com:gem/oq-engine into disagg-2
Merged from disagg-2