Improve code related to node (#4383)

* Make full use of node

implement local node

fix bugs mentioned in comments

* Add more tests

* Use more specific exception handling

* fix, lint

* fix for py2.x

python/ray/workers/default_worker.py

@@ -66,14 +66,6 @@ parser.add_argument(
 if __name__ == "__main__":
     args = parser.parse_args()
 
-    info = {
-        "node_ip_address": args.node_ip_address,
-        "redis_address": args.redis_address,
-        "redis_password": args.redis_password,
-        "store_socket_name": args.object_store_name,
-        "raylet_socket_name": args.raylet_name,
-    }
-
     ray.utils.setup_logger(args.logging_level, args.logging_format)
 
     ray_params = RayParams(
@@ -89,12 +81,7 @@ if __name__ == "__main__":
         ray_params, head=False, shutdown_at_exit=False, connect_only=True)
     ray.worker._global_node = node
 
-    # TODO(suquark): Use "node" as the input of "connect".
-    ray.worker.connect(
-        info,
-        redis_password=args.redis_password,
-        mode=ray.WORKER_MODE,
-        load_code_from_local=args.load_code_from_local)
+    ray.worker.connect(node, mode=ray.WORKER_MODE)
 
     error_explanation = """
   This error is unexpected and should not have happened. Somehow a worker