Added 'auth_uri' key to neutron.conf on controller node

I added configuration of the 'auth_uri' key to neutron.conf on the
controller node to eliminate a warning about potential endpoint
authentication issues in the Neutron server log.

Change-Id: I977fe53964a4a17fb0e28f0487f60bcffa828b1f
backport: havana
Closes-Bug: #1264166
Merge "Added 'auth_uri' key to neutron.conf on controller node"