https://github.com/rackerlabs/otter/blob/master/otter/rest/groups.py#L321 seems to call `modify_state`?

Mainly I'm concerned with modify_state because it's the thing that does locking, otherwise calling obey_config_change pokes at the state table without getting a lock, so if some servers come up at around the time the group is force deleted, it's more likely we'd lose track of them.

If these pass the system tests, I'm fine with merging this so long as another issue to fix it is filed high priority/next on the list of things to do.  :)