Cancelling `ModelSendAsync` can close the connection when it shouldn't

[lukebakken]

Describe the bug

Reported here: #1720 (comment)

Reproduction steps

• Pass cancellation token to BasicConsumeAsync that will close in the future.
• Notice that the connection is closed:

  CloseReason: AMQP close-reason, initiated by Library, code=541, text='A task was canceled.', classId=0, methodId=0, exception=System.Threading.Tasks.TaskCanceledException: A task was canceled.
  at RabbitMQ.Client.Impl.BasicConsumeAsyncRpcContinuation.HandleCommandAsync(IncomingCommand cmd)
  at RabbitMQ.Client.Impl.Channel.HandleCommandAsync(IncomingCommand cmd, CancellationToken cancellationToken)
  at RabbitMQ.Client.Framing.Connection.ProcessFrameAsync(InboundFrame frame, CancellationToken cancellationToken)
  at RabbitMQ.Client.Framing.Connection.ReceiveLoopAsync(CancellationToken mainLoopCancellationToken)
  at RabbitMQ.Client.Framing.Connection.MainLoop()
  

Expected behavior

Connection should not close in this case.

Additional context

#1720 (comment)

[ZajacPiotr98]

I think passing already cancelled cancellation token will trigger exception already on the await _rpcSemaphore.WaitAsync(k.CancellationToken). The problem occurs when it's passed to the Connection.

Any exception thrown from the HandleCommandAsync method of AsyncRpcContinuation is causing closing the Connection.

[lukebakken]

@ZajacPiotr98 if you have time to test #1753, I would appreciate it. Thanks!