Make actor handles work in Python mode. (#2283)

* Make actor handles work in local mode.

* Add test for actor handles in local mode.

test/runtest.py

@@ -1189,6 +1189,16 @@ class PythonModeTest(unittest.TestCase):
         test_array[0] = -1
         assert_equal(test_array, test_actor.get_array.remote())
 
+        # Check that actor handles work in Python mode.
+
+        @ray.remote
+        def use_actor_handle(handle):
+            array = np.ones(10)
+            handle.set_array.remote(array)
+            assert np.alltrue(array == ray.get(handle.get_array.remote()))
+
+        ray.get(use_actor_handle.remote(test_actor))
+
 
 class ResourcesTest(unittest.TestCase):
     def tearDown(self):