Move to oslo.messaging

Just an experiment, don't take it seriously =)

Things i found odd:
 - eventlet is not working. Just did not pull the incoming queue.
 - kombu should be in oslo.messaging requirements, not mistrel's
 - i wasn't able to find how to scope cfg.CONF on a group level and still be able to .register_opts() on it. Anyway, it seems like nova is ok with groupless configs.