Stopgap fix:  AI's won't use more and more power.

With new APC zone methods having non-machines use_power in their master_contrller called processes means
that they don't update the zone's flag to recalculate power usage and will continue to increase the
per-tick power usage each tick.  AI should be the only problem with this unless robutts have a life() tick
to use_power on the area when inside a charger or something really stupid.