Add default_volume_type as cinder api parameter

Adds a parameter to set the default_volume_type for the cinder api.
Cinder-api uses this value if in CLI the parameter '--volume-type' is not
given.

Change-Id: I6cdad0a90d249bdaa2729d201cf10d3b16dd96a1
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.)

Change-Id: I957d81647cd0320a52be00dceff23692ba208017
Merge "Add default_volume_type as cinder api parameter"