Guaranteed Delivery not working if no timeout is set

When guaranteed delivery is activated but no timeout is set for publisher acknowledgement waitForConfirmsOrDie will never return.
This is because the close is not triggered on the channel even if the connection is closed when an exception is thrown in the return listener.

This is also the reason why the integration test for the producer does not complete.

The provided pull request fixes this issue in that way that it will just remember that a basic.return has been received and will throw the exception after waitForReturnOrDie completes