Convert local scheduler messages to flatbuffers (#340)

* use flatbuffer messages for local scheduler

* make sure constructor gets called for C++ object ObjectInfoT

* fix typo

* fix Robert's comments

* Small change to actor test.

* fix valgrind error

* linting

* free notification

* fix

* valgrind

* fix valgrind

* fix other bugs

* valgrind fix

* fixes

* more fixes

* Small changes to comments.

test/actor_test.py

@@ -661,7 +661,7 @@ class ActorsWithGPUs(unittest.TestCase):
       for _ in range(n):
         Actor()
 
-    ray.get([create_actors.remote(10) for _ in range(10)])
+    ray.get([create_actors.remote(num_gpus_per_scheduler) for _ in range(num_local_schedulers)])
 
     @ray.actor(num_gpus=1)
     class Actor(object):
@@ -674,5 +674,7 @@ class ActorsWithGPUs(unittest.TestCase):
     with self.assertRaises(Exception):
       Actor()
 
+    ray.worker.cleanup()
+
 if __name__ == "__main__":
   unittest.main(verbosity=2)