[Bug] PostgresQueueDao processAllUnacks thread dies silently

[pmchung]

Describe the bug
When conductor loses connection to postgres for a period of time and the newSingleThreadScheduledExecutor that executes processAllUnacks throws an exception (due to loss of connection or any other reason), no more task are scheduled.

Details
Conductor version: All
Persistence implementation:Postgres
Queue implementation: Postgres
Lock: Redis
Workflow definition:
Task definition:
Event handler definition:

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
The thread should continue attempts to execute processAllUnacks as postgres connection will eventually recover.

Screenshots
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Additional context
https://stackoverflow.com/questions/6894595/scheduledexecutorservice-exception-handling