multi rbd: add opts, deprecate glance_api_version

- Add all cinder rbd params (multi-backends)
- Update documentation/tests
- Deprecate glance_api_version to avoid duplicate definition
  with cinder::glance class.
  (use glance_api_version of cinder::glance class instead.)

(cherry picked from commit dda201af2aa9f4fdca1b46bbeeeea6821ba6b637)

Change-Id: I237ea1ae7a9a1a67272b4ec705d832daef1bc5c7
Merge "multi rbd: add opts, deprecate glance_api_version" into stable/havana