MessageAndSessionPump closes the connection on the receipt of SIGTERM.

## Actual Behavior
1. On receipt of SIGTERM, MessageAndSessionPump closes the connection to service bus even though close/closeAsync is not called on queueClient.
2. I have a spring boot application that handles the SIGTERM for graceful shutdown - as part of graceful shutdown, the code calls queueClient.closeAsync to close the connection to Azure Service bus. Unfortunately, MessageAndSessionPump closes the connection (log: Closing message and session pump on entity 'my_queue') much ahead of queueClient.closeAsync call.

## Expected Behavior
1. MessageAndSessionPump should not close the connection until the queueClient.closeAsync is called.

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