message: [tf.data service] Add test for fixed-seed shuffling.
  The test demonstrates that when a fixed seed is set, each tf.data service worker will shuffle the dataset in the same order.
diff: @@ -144,13 +144,15 @@ class DataServiceOpsTest(data_service_test_base.TestBase,
  self.assertDatasetProduces(
  ds, [v1, v2, default_value], requires_initialization=True)
  - @combinations.generate(test_base.default_test_combinations())
  - def testDifferentShuffleOrders(self):
  + @combinations.generate(
  + combinations.times(test_base.default_test_combinations(),
  + combinations.combine(shuffle_seed=[None, 10])))
  + def testShuffleOrder(self, shuffle_seed):
  random_seed.set_random_seed(None)
  num_elements = 100
  cluster = data_service_test_base.TestCluster(num_workers=2)
  ds = dataset_ops.Dataset.range(num_elements)
  - ds = ds.shuffle(num_elements)
  + ds = ds.shuffle(num_elements, seed=shuffle_seed)
  ds = self.make_distributed_dataset(ds, cluster)
  output = self.getDatasetOutput(ds)
  @@ -164,7 +166,10 @@ class DataServiceOpsTest(data_service_test_base.TestBase,
  second_order[element] = len(second_order)
  else:
  first_order[element] = len(first_order)
  + if shuffle_seed is None:
  self.assertNotEqual(first_order, second_order)
  + else:
  + self.assertEqual(first_order, second_order)
  @combinations.generate(test_base.default_test_combinations())
  def testMultipleEpochs(self):
  