Always call update_use_power() instead of directly setting the use_power var.

- This will let us react to the change appropriately.
- While we're here, lets define some constants so we can stop using bare numbers.
- Always use those constants when calling update_use_power()

code/modules/holodeck/HolodeckControl.dm

@@ -224,7 +224,7 @@
 			damaged = 1
 			loadProgram(powerdown_program, 0)
 			active = 0
-			use_power = 1
+			update_use_power(USE_POWER_IDLE)
 			for(var/mob/M in range(10,src))
 				M.show_message("The holodeck overloads!")
 
@@ -271,7 +271,7 @@
 			linkedholodeck.gravitychange(1)
 
 		active = 0
-		use_power = 1
+		update_use_power(USE_POWER_IDLE)
 
 
 /obj/machinery/computer/HolodeckControl/proc/loadProgram(var/prog, var/check_delay = 1)