Exception during start_inference_process causes hung worker

[db0]

When an exception occurs in horde_worker_regen.process_management.worker_entry_points:start_inference_process the worker ends up in a stuck state where it's endlessly rotating models between its queues.

Also see:

• Unhandled exception when github drops connection during model reference retrieval hordelib#152
• Multiprocessing leads to disk IO racing w/ model reference  horde-model-reference#72