Removed 'rpc' and 'notifier' incubator modules

Port to oslo.messaging is done, so remove now unused pieces from the
tree.

Also removed obsolete bin/quantum-rpc-zmq-receiver. It comes from old
days of oslo-rpc, it was reimplemented later as
openstack/common/rpc/zmq_receiver.py in oslo-incubator, and we've
removed the whole tree for old RPC layer anyway.

blueprint oslo-messaging

Change-Id: If7155c59c8ef58d06164938998180f3367b9bb16
Merge "Removed 'rpc' and 'notifier' incubator modules"