We've incorrectly embedded the project ID in our block storage
endpoint override for Rackspace Public Cloud, which leads to a 404
Not Found response since the SDK appends the supplied project_id
already. Removing this allows to use latest versions of the
OpenStack CLI/SDK for volume management in Rackspace Public Cloud,
so long as we pin python-cinderclient<8 (for v2 API support).
Change-Id: If37f1a848ec4d3128784ed28068bfae9f06e2f14
7740dfef14