Make Keystone return v3 as part of the version api

The keystone "get version" api currently fails to list v3
as a supported api.  It should now do this, along with v2 (which is,
of course, still supported)

Fixes Bug #1148186

Change-Id: Ie88bf941123702d2f7e2ecf6cecb1fa937ca1e52
Merge "Make Keystone return v3 as part of the version api"