Fix update snapshot-quotas on delete.

The merge from stable to RC of the snapshot quota
fixes missed the new CONF usage and as a result the
setting was always ignored on delete and therefore
quotas were not decremented on delete.

This patch changes CONF back to FLAGS for that call and
resolves the issue.

Fixes bug: 1173365

Change-Id: I7af69d5078ebcc5547e08d543a2dcfd0ca3f6c4b