Define a Node class to manage Ray processes. (#3733)

* Implement Node class and move most of services.py into it.

* Wait for nodes as they are added to the cluster.

* Fix Redis authentication bug.

* Fix bug in client table ordering.

* Address comments.

* Kill raylet before plasma store in test.

* Minor

python/ray/workers/default_worker.py

@@ -8,7 +8,6 @@ import traceback
 
 import ray
 import ray.actor
-from ray.parameter import RayParams
 import ray.ray_constants as ray_constants
 import ray.tempfile_services as tempfile_services
 
@@ -76,15 +75,8 @@ if __name__ == "__main__":
     # Override the temporary directory.
     tempfile_services.set_temp_root(args.temp_dir)
 
-    ray_params = RayParams(
-        node_ip_address=args.node_ip_address,
-        redis_address=args.redis_address,
-        redis_password=args.redis_password,
-        plasma_store_socket_name=args.object_store_name,
-        raylet_socket_name=args.raylet_name,
-        temp_dir=args.temp_dir)
-
-    ray.worker.connect(ray_params, info, mode=ray.WORKER_MODE)
+    ray.worker.connect(
+        info, redis_password=args.redis_password, mode=ray.WORKER_MODE)
 
     error_explanation = """
   This error is unexpected and should not have happened. Somehow a worker