ironic client to use os_region_name if provided

Currently ironicclient does not pass OS_REGION_NAME to Keystone client.
That will cause problems in multiregion deployments.

Modified ironicclient to consider using OS_REGION_NAME if provided.

Closes-Bug: #1314159

Change-Id: I885e57973ccec64471fe2ba5fecfab2224829787
Merge "ironic client to use os_region_name if provided"