[Bug] PostgresQueueDao processAllUnacks thread dies silently

**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:
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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