minor fix: omnet require str as id for each actor

Author: StefanodiTerlizzi

pycarlanet/listeners/ActorManager.py

@@ -60,7 +60,7 @@ def add_carla_actor_to_omnet(self, actor:carla.Actor):
         """
         print(f"add_carla_actor_to_omnet, id {actor.id} -> {actor}")
         #TODO check if is correct and uncomment
-        self._carlanet_actors[actor.id] = CarlanetActor(actor, True) 
+        self._carlanet_actors[f'{actor.id}'] = CarlanetActor(actor, True) 
 
         #TODO check if necessary
         #if actor.id in self._carlanet_actors: