add script to manage cinder backup lifecycle

In order to enable and disable the backup service, the python-cinderlcient had to be installed to talk to the api.

In order to evaluate how many backups are acutally running on the backup service, the database is accessed directly from the script, because the information are not provided via the API. This is implmenented analog the the cinder-manage script.

For both operations, the configuration from the cinder.conf is used.

Contributes to yaook/operator#301 (closed)