Explicitly define "auth_region" in Neutron metadata_agent.ini

The default value for "auth_region" assumes "RegionOne" rather
than "regionOne" which causes the metadata agent to generate
authentication errors.

Change-Id: I0d3395a215eea7b3e3a9760a81e5f72a6bf523a4
Closes-Bug: #1259344
(cherry picked from commit 534aeb30c7a2c38a2f4294eea62c81e501bc9f2a)
Merge "Explicitly define "auth_region" in Neutron metadata_agent.ini" into stable/havana