Fixed pytorch cpu parallelism error

Author: p-christ

agents/actor_critic_agents/A3C.py

@@ -109,6 +109,7 @@ def set_seeds(self, worker_num):
 
     def run(self):
         """Starts the worker"""
+        torch.set_num_threads(1)
         for ep_ix in range(self.episodes_to_run):
             with self.optimizer_lock:
                 Base_Agent.copy_model_over(self.shared_model, self.local_model)