Add CloudRegion helper method for arbitrary endpoints
Add CloudRegion helper method for arbitrary endpoints

Sometimes you are faced with dealing with a non-standard service and
you don't want to type

   c.session.auth.get_endpoint(
      c.session, service_type='example-service-type',
      region_name=c.config.region_name, interface=c.config.interface))

Add a helper method so you don't have to.

Change-Id: I50d179abc528a884bae4b4af72936b634b26e93b

dtroyer/python-openstacksdk,stackforge/python-openstacksdk,openstack/python-openstacksdk,openstack/python-openstacksdk,stackforge/python-openstacksdk,dtroyer/python-openstacksdk