Accept 201 status code on POST

On POST requests, keystone should return '201 Created' according to
api docs.

Related to but not dependent on:
https://bugs.launchpad.net/keystone/+bug/1131119

Change-Id: I04c398ad7946f5ddcfd2059e4f8d97608e5d0ed3
Merge "Accept 201 status code on POST"