cinder_ceilometer: use the class

Instead of using cinder_config, we should use cinder::ceilometer class
which configure the notification_driver by default:
cinder.openstack.common.notifier.rpc_notifier

Change-Id: I12253a21f5f41cf418408eecf9a78b18f6c16c30
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge "cinder_ceilometer: use the class"