Sync latest rpc changes from oslo-incubator

Includes these commits:

 3006787 Sanitize passwords in _safe_log
 c37f6aa Add support for heartbeating in the kombu RPC driver
 323e465 Add conditional exception reraise
 dea334a Replace sys.exit by a RPCException
 719eba4 Don't reconnect to exclusive fanout consumers.
 22ec8ff Make AMQP based RPC consumer threads more robust
 13650b1 rpc: remove some unused serialization code
 e204885 Optionally reject messages on exception.
 688832f Remove unused zmq relay functionality

Change-Id: I8629c271bc00571783f9b77ec36034945df9a583
Merge "Sync latest rpc changes from oslo-incubator"