Ensure routing key is specified in the address for a direct producer

Porting this fix from oslo.messaging.  This fixes the impl_qpid.py
driver to allow it to work with the latest stable upstream QPID broker
(version 0.28).  See the Apache Qpid Jira bug
https://issues.apache.org/jira/browse/QPID-5557

Change-Id: If71f78e50f8a9b3acfd1e9d02c8271f17c4ebee7
Closes-Bug: #1300318
(cherry picked from commit a90f0c6cfc44bc3c3fecec2f3b7281902cd6ec19)