Remove usage of QueueingConsumer in tests

[acogoluegnes]

QueueingConsumer has been deprecated in 4.0.0, all tests relying on it should use an alternative.

[michaelklishin]

Good idea.

[acogoluegnes]

Many tests use QueueingConsumer and a refactoring wouldn't bring much, so there's now a QueueingConsumer class in the test directory. I won't ship with the client binary.