Rackspace only has v1 in the catalog but run a cinder that supports
v2. Since SDK doesn't have support for v1 at all, update our
vendor config with an endpoint override for their block-storage
service.
As a special bit of hell, the url needs the project_id appended
which we cannot do with our normal format substitutions, so put in
YET ANOTHER Rackspace specific workaround logic.
Story: 2007459
Task: 39146
Change-Id: I4e6485b936b6b7303b6463cbacd3bf98746fc5e1
c6c69fc474