message: Increase rtol in callableForTestModelRestoreCallback test
  of multi_worker_callback_test to reduce flakiness.
diff: @@ -232,7 +232,7 @@ class KerasMultiWorkerCallbackTest(test_base.IndependentWorkerTestBase,
  test_obj.assertAllClose(
  history_after_one_more_epoch.history,
  history_after_loading_weight_and_one_more_epoch.history,
  - rtol=6e-6)
  + rtol=5e-5)
  # Verify the temp files are indeed removed (no trace left behind).
  for filepath in filepaths:
  @@ -266,7 +266,7 @@ class KerasMultiWorkerCallbackTest(test_base.IndependentWorkerTestBase,
  test_obj.assertAllClose(
  history_after_one_more_epoch.history,
  history_after_model_restoring_and_one_more_epoch.history,
  - rtol=5e-6)
  + rtol=5e-5)
  history_one_more_epoch_without_model_restoring = model.fit(
  x=train_ds, epochs=1, steps_per_epoch=steps)
  @@ -274,7 +274,8 @@ class KerasMultiWorkerCallbackTest(test_base.IndependentWorkerTestBase,
  # Ensuring training for another epoch gives different result.
  test_obj.assertNotAllClose(
  history_after_model_restoring_and_one_more_epoch.history,
  - history_one_more_epoch_without_model_restoring.history)
  + history_one_more_epoch_without_model_restoring.history,
  + rtol=5e-5)
  @staticmethod
  def callableForTestUnmatchedModelFile(model, test_obj, train_ds, num_epoch,
  