cyclades: Fix use of disk_template in stats

The 'disk_template' attribute has been moved from the 'Flavor' model to
the 'VolumeType' object. Update Cyclades statistics mechanism to reflect
this change.
astakos: Fix stats for new projects

The recent changes in the Astakos projects implementation changed the
contents of the 'quotaholder_app_holding' table. This table now contains
holdings for both users and projects. Also, the 'holder' column contains
user or project UUIDs, prefixed by 'user:' or 'project:' respectively.
This commit updates the stats mechanism in order to reflect the
aforementioned changes.