If a service record is gone from the DB the _report_state method
will log a generic traceback every time the report interval runs,
which is every 10 seconds by default. This gets pretty noisy and
the error logged isn't very useful. One could get into this state
by deleting the service record in the API before stopping the actual
process that is running.
This simply handles the ServiceNotFound error and logs a more useful
error message without the noisy traceback.
Change-Id: If0336001fbe39922a199756db0803121cbe560af
Related-Bug: #1813147
945d662d4f