Sync rpc from oslo-incubator.

Changes include:

 * Fix Copyright Headers - Rename LLC to Foundation
 * Preserve exceptions in impl_zmq.
 * Don't log a traceback on rpc call timeout.
 * Redis-based matchmaker
 * AMQP: skip duplicate messages
 * some other minor fixes / cleanups

Fix bug 1154232.

Change-Id: I8afb6b9a919fca34b4a93f7fad1551a023eba6b2
Merge "Sync rpc from oslo-incubator."