declare queue in producer, fixes lp#1338732

fixes https://bugs.launchpad.net/oslo/+bug/1338732

When rabbit dies, the RPC producer may publish a reply before the consumer reconnects and recreates the queue.  The current code would publish to an exchange without a queue and thus drop the message, leading to RPC failure.  The fix here always creates the queue on both sides before publishing.  See the LP bug for more details.