Suspend SSmachines subsystem while we are initializing map templates.

- Adds the capability to "suspend" a subsystem while we're loading something.

code/controllers/subsystem.dm

@@ -203,3 +203,15 @@
 //usually called via datum/controller/subsystem/New() when replacing a subsystem (i.e. due to a recurring crash)
 //should attempt to salvage what it can from the old instance of subsystem
 /datum/controller/subsystem/Recover()
+
+// Suspends this subsystem from being queued for running.  If already in the queue, sleeps until idle. Returns FALSE if the subsystem was already suspended.
+/datum/controller/subsystem/proc/suspend()
+	. = (can_fire > 0) // Return true if we were previously runnable, false if previously suspended.
+	can_fire = FALSE
+	// Safely sleep in a loop until the subsystem is idle, (or its been un-suspended somehow)
+	while(can_fire <= 0 && state != SS_IDLE)
+		stoplag() // Safely sleep in a loop until 
+
+// Wakes a suspended subsystem.
+/datum/controller/subsystem/proc/wake()
+	can_fire = TRUE

code/modules/maps/tg/map_template.dm

@@ -41,6 +41,7 @@
 
 	var/prev_shuttle_queue_state = SSshuttles.block_init_queue
 	SSshuttles.block_init_queue = TRUE
+	var/machinery_was_awake = SSmachines.suspend() // Suspend machinery (if it was not already suspended)
 
 	var/list/atom/atoms = list()
 	var/list/area/areas = list()
@@ -74,6 +75,8 @@
 		var/area/A = I
 		A.power_change()
 
+	if(machinery_was_awake)
+		SSmachines.wake() // Wake only if it was awake before we tried to suspended it. 
 	SSshuttles.block_init_queue = prev_shuttle_queue_state
 	SSshuttles.process_init_queues() // We will flush the queue unless there were other blockers, in which case they will do it.