Fix race condition in QueueChannelTests#testSimpleSendAndReceive()

The test verification uses ArgumentCaptor on logger.debug(), but there is no guaranty that all those debugs are called in the desired order. It isn't predictable because we use channel.receive() from separate Thread, hence we can receive a Message (and therefore logger.debug("postReceive on channel '" + this + "', message: " + message)) before the invocation for logger.debug("postSend (sent=" + sent + ") on channel '" + this + "', message: " + message).

Don't see reason to verify those logs in this test.