As described in #3565, units don't necessarily stay stopped when told to stop as part of a formation. The problem is that the formation continues to move, and later tells its members to hurry and catch up. This patch tells the formation controller itself to stop, so it fixes both issues mentioned in the trac ticket.

Verify that the bugs are fixed.

(You can uncomment the visual actor in template_formation to see a flag representing the formation controller, although I think I had to tweak a few things to get it to work.)