Simplify total cost calc

src/engine/gameManager/ForgeManager.java

@@ -160,8 +160,7 @@ public enum ForgeManager implements Runnable {
             workOrder.total_to_produce *= workOrder.slots_used;
 
             workOrder.production_cost = calcProductionCost(workOrder);
-            workOrder.production_cost_total.putAll(workOrder.production_cost);
-            workOrder.production_cost_total.forEach((key, value) -> workOrder.production_cost_total.put(key, value * workOrder.total_to_produce));
+            workOrder.production_cost.forEach((key, value) -> workOrder.production_cost_total.put(key, value * workOrder.total_to_produce));
 
             // Withdraw gold and resource costs.  Availability has previously been validated.