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**Description**

Related to the discussion here: https://github.com/apache/airflow/pull/8553#discussion_r416136954

Allow user to define expected terminal state. e.g. `JOB_STATE_CANCELLED` could be not treated as failure but expected terminal state.


<!-- A short description of your feature -->


start_template_hook = dataflow_mock.return_value.start_template_dataflow
        sync_operator.execute(None)
        assert dataflow_mock.called
        expected_options = {
            "project": "test",
            "stagingLocation": "gs://test/staging",
            "tempLocation": "gs://test/temp",
            "zone": "us-central1-f",
            "EXTRA_OPTION": "TEST_A",
        }
        start_template_hook.assert_called_once_with(
            job_name=JOB_NAME,
            variables=expected_options,
            parameters=PARAMETERS,
            dataflow_template=TEMPLATE,
            on_new_job_callback=mock.ANY,
            project_id=TEST_PROJECT,
            location=TEST_LOCATION,
            environment={"maxWorkers": 2},
            append_job_name=True,
        )
    @mock.patch("airflow.providers.google.cloud.operators.dataflow.DataflowTemplatedJobStartOperator.defer")
    @mock.patch("airflow.providers.google.cloud.operators.dataflow.DataflowTemplatedJobStartOperator.hook")
    def test_execute_with_deferrable_mode(self, mock_hook, mock_defer_method, deferrable_operator):