Rather than our freeform way of listing response codes in our
api-ref, we should be using the os-api-ref extension option to
get nicely formatted response code listings.
https://docs.openstack.org/os-api-ref/latest/usage.html#rest-status-code
Change-Id: Ibafafa2f9c3b301b5cdd9b1cb3b8b6d678faa731