Add a hard off for NPC scaling for Merc/Bot

They don't need it. We may want to add this to actually be in the DB for
normal NPCs in the future.

zone/npc_scale_manager.cpp

@@ -26,6 +26,9 @@
  */
 void NpcScaleManager::ScaleNPC(NPC * npc)
 {
+	if (npc->IsSkipAutoScale())
+		return;
+
 	int8 npc_type       = GetNPCScalingType(npc);
 	int  npc_level      = npc->GetLevel();
 	bool is_auto_scaled = IsAutoScaled(npc);
@@ -621,4 +624,4 @@ bool NpcScaleManager::ApplyGlobalBaseScalingToNPCDynamically(NPC *&npc)
 	auto results = database.QueryDatabase(query);
 
 	return results.Success();
-}
+}