PersistenceManager availability check permanently fails with uncaught exception

Currently PersistenceManagerImpl#pollStoreAvailability utilises a try/finally block, meaning any runtime exceptions thrown during the availability checks will cause the CompletionStage to fail. Consequently, pollStoreAvailability won't be executed again as it uses NonBlockingManager#scheduleWithFixedDelay which does not reschedule a CompletionStage that has failed.

Additional logging should be added to polStoreAvailability to make it clear that such exceptions have been thrown.