Update response codes for authentication API reference
Update response codes for authentication API reference

The API reference for authentication and validation APIs listed some
HTTP status codes that keystone never actually uses. This commit
updates those examples to be more explicit about what keystone
returns.

Change-Id: If5cb27d1cc3fc8d8c57ccb47d1a99ba07aecba83

openstack/keystone,mahak/keystone,mahak/keystone,mahak/keystone,openstack/keystone,openstack/keystone