Only loop NPC movement if the NPC has a looping path assigned

Allows paths to terminate.
Also fixes a bug where follower NPCs sometimes oscillate their positions.

src/Transport.hpp

@@ -33,6 +33,7 @@ struct NPCPath {
     int speed;
     int escortTaskID;
     bool isRelative;
+    bool isLoop;
 };
 
 namespace Transport {