Remove Cinder v2 RBAC tests

This PS removes Cinder v2 RBAC tests, as the policy tests can
be performed via the v3 API. Policy enforcement doesn't change
between v2 and v3 APIs, so we should only test the latest API.

Change-Id: Id0421a958a2c4b087bd7a886ae088eac5fe3c79a
23 files changed