Improve removal of job from the queue when job is deleted

refs #66

- 'delete_job' removes job id record from the queue list.
  This helps to diagnose cases when job data was removed by Redis OOM handler
  vs explicitly deleted by user.
- Use single hash for storing all job data on Redis server.
- Removed 'NS_METADATA_SUFFIX' constant.

Change-Id: Ib1a90d18f1fb05dee1ad093d016567cdf53d242e