On shutdown, a single job can never finish

[tazlin]

I have observed that it is possible, following a SIGINT (control+c) shutdown initiation that sometimes a single job can never finish, with the following observations:

• The job was stuck for a long (>1hr) time previous to the shutdown
• The model for that job was stuck in PRELOADED_MODEL for that entire time
• Even once it was the final job left, and that process the last process, it still did not start

The worker only will end if force killed or once deadlock protection kicks in.

I can attest that this does not happen regularly, but I have observed it at least 3 (of maybe 15) shutdowns.