**Apache Airflow version**:
2.0.1

**Kubernetes version**:
Server Version: version.Info{Major:"1", Minor:"18+", GitVersion:"v1.18.9-eks-d1db3c", GitCommit:"d1db3c46e55f95d6a7d3e5578689371318f95ff9", GitTreeState:"clean", BuildDate:"2020-10-20T22:18:07Z", GoVersion:"go1.13.15", Compiler:"gc", Platform:"linux/amd64"}

**What happened**:
Clearing a failed subdag task with Downstream+Recursive does not automatically set the state of the parent dag to 'running' so that the downstream parent tasks can execute.

The work around is to manually set the state of the parent dag to running after clearing the subdag task

**What you expected to happen**:
With airflow version 1.10.4 the parent dag was automatically set to 'running' for this same scenario

**How to reproduce it**:
- Clear a failed subdag task selecting option for Downstream+Recursive
- See that all down stream tasks in the subdag as well as the parent dag have been cleared
- See that the parent dag is left in 'failed' state. 

tests/models/test_dag.py
"""
        Tests if fractional seconds are stored in the database
        """
        dag_id = "test_fractional_seconds"
        dag = DAG(dag_id=dag_id)
        dag.schedule_interval = '@once'
        dag.add_task(BaseOperator(task_id="faketastic", owner='Also fake', start_date=TEST_DATE))
        start_date = timezone.utcnow()
        run = dag.create_dagrun(
            run_id='test_' + start_date.isoformat(),
            execution_date=start_date,
            start_date=start_date,
            state=State.RUNNING,
            external_trigger=False,
        )
        run.refresh_from_db()
        assert start_date == run.execution_date, "dag run execution_date loses precision"
        assert start_date == run.start_date, "dag run start_date loses precision "
        self._clean_up(dag_id)
    def test_pickling(self):
        test_dag_id = 'test_pickling'
        args = {'owner': 'airflow', 'start_date': DEFAULT_DATE}
        dag = DAG(test_dag_id, default_args=args)
        dag_pickle = dag.pickle()
        assert dag_pickle.pickle.dag_id == dag.dag_id
    def test_rich_comparison_ops(self):
        test_dag_id = 'test_rich_comparison_ops'
        class DAGsubclass(DAG):