Mitigates job_status dict change during iteration
Mitigates job_status dict change during iteration

If job_status changed during iteration, _clean queried on keys no longer in the dictionary
See https://bugs.launchpad.net/monasca/+bug/1476313
This does not fix this bug, it only mitigates one of the symptoms.
I am not sure that items() is thread safe, but it does reduce the window of time during which problems can occur
  by collecting all values upfront.

Change-Id: Ibe206f45ff308a8b6d04eda28367846105414491

sapcc/monasca-agent,sapcc/monasca-agent,sapcc/monasca-agent