Rename policy auth for V3 os-fixed-ips

Renames name used to for policy authorisation for the
V3 os-fixed-ips to os-fixed-ips with a "v3:" prefix (as
per ML discussion)

Change-Id: Ia599c29d7f45153ef47605b6e2a7061fc28ff7cc
Merge "Rename policy auth for V3 os-fixed-ips"