Add tests for rabbit driver wire protcol

Add two test cases:

  - send messages using the rabbit driver and check that the message
    gets sent to the expected queue in the expected format

  - send messages to a given queue in the correct format and check that
    we can happily consume them using the rabbit driver

i.e. these are tests that check that the driver sends and receives
messages according to the wire protocol.

Change-Id: I6a48085585981b17609b31f216bdca438e90e068
Merge "Add tests for rabbit driver wire protcol"