hi,team:

    my dag is 1 minute schedule,one parts dag state is success,but tasks state is not yet started in a dag:

![image](https://user-images.githubusercontent.com/41068725/116344664-357d8780-a819-11eb-8010-c746ffdfdbcc.png)


   how can to fix it?
tests/www/test_app.py
@conf_vars(
        {
            ('core', 'sql_alchemy_pool_enabled'): 'True',
            ('core', 'sql_alchemy_pool_size'): '3',
            ('core', 'sql_alchemy_max_overflow'): '5',
            ('core', 'sql_alchemy_pool_recycle'): '120',
            ('core', 'sql_alchemy_pool_pre_ping'): 'True',
        }
    )
    @dont_initialize_flask_app_submodules
    @pytest.mark.backend("mysql", "postgres")
    def test_should_set_sqlalchemy_engine_options(self):
        app = application.cached_app(testing=True)
        engine_params = {'pool_size': 3, 'pool_recycle': 120, 'pool_pre_ping': True, 'max_overflow': 5}
        assert app.config['SQLALCHEMY_ENGINE_OPTIONS'] == engine_params
    @conf_vars(
        {
            ('webserver', 'session_lifetime_minutes'): '3600',
        }
    )
    @dont_initialize_flask_app_submodules
    def test_should_set_permanent_session_timeout(self):
        app = application.cached_app(testing=True)
        assert app.config['PERMANENT_SESSION_LIFETIME'] == timedelta(minutes=3600)
    @conf_vars({('webserver', 'cookie_samesite'): ''})
    @dont_initialize_flask_app_submodules
    def test_correct_default_is_set_for_cookie_samesite(self):
        app = application.cached_app(testing=True)
        assert app.config['SESSION_COOKIE_SAMESITE'] == 'Lax'
class TestFlaskCli: