Sync rpc from oslo-incubator.

This includes rpc api namespace support, some minor configuration
related fixes, and the redis based matchmaker for use with impl_zmq.

Change-Id: I9fc826a498461417afe8b2a923edac8d68c2c18f
Imported Translations from Transifex

Change-Id: Ib7dd5ace2eaf2060ea0a65ff9100a1fdbc10ccdf
Merge "Sync rpc from oslo-incubator."