Remove support for drivers in the Cinder.conf default section

This blueprint is specifically for the puppet-cinder module to remove support for drivers in the cinder.conf default sections in correspondence with this blueprint in Cinder https://blueprints.launchpad.net/cinder/+spec/shared-backend-config I'm setting this up as a separate blueprint for puppet since the cinder blueprint includes a much wider scope. For Newton, this blueprint will only add depreciation warnings to the puppet module, actual removal will wait for the proper depreciation time (I believe 'O')