GEODE-9887: Fix for deadlock during server shutdown

[jvarenina]

This deadlock happens when server is shutdown gracefully.
"Distributed system shutdown hook" thread initiates shutdown threads
"ConcurrentParallelGatewaySenderEventProcessor Stopper Thread"
and waits for them to finish.
Every "ConcurrentParallelGatewaySenderEventProcessor Stopper Thread"
then set flag AckReaderThread.shutdown indicating that AckReaderThread
should be also shutdown and waits for it by joining the threads for max 15 seconds.
The "AckReaderThread for : Event Processor for GatewaySender_sender"
thread blocks during shutdown because it tries to acquire the lock that was
already acquired by "Distributed system shutdown hook" thread.
This deadlock only last for 15 seconds, because thread join
will expire for all "ConcurrentParallelGatewaySenderEventProcessor
Stopper Thread" threads forcing them to finish. Because these threads finished,
the "Distributed system shutdown hook" can continue the execution,
release the lock and conclude the shutdown. The problem here is that
delay of 15 seconds can cause traffic loss if read-timeout on clients
is configured to lower value.

The fix:
When exception happen in AckReaderThread due to shutdown of the server
(e.g. CacheClosedException) then check if shutdown is already ongoing before
trying to acquire the lock and initiate shutdown of the dispatcher threads.
When server is shutting down that means that dispatcher threads are already
in the process of shutting down and there is no need for AckReaderThread
to initiate the same thing again.

For all changes:

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• Does gradlew build run cleanly?

• Have you written or updated unit tests to verify your changes?

• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?

[nabarunnag]

Looks good to me