Fix: Train running sounds should only be produced for engine parts.

Wagons were excluded, but articulated parts and second multihead parts should be excluded too.

src/vehicle.cpp

@@ -1034,7 +1034,7 @@ void CallVehicleTicks()
 				/* Check vehicle type specifics */
 				switch (v->type) {
 					case VEH_TRAIN:
-						if (Train::From(v)->IsWagon()) continue;
+						if (!Train::From(v)->IsEngine()) continue;
 						break;
 
 					case VEH_ROAD: