**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
"""
        Test scheduling a dag where there is a prior DagRun
        which has the same run_id as the next run should have
        """
        delta = datetime.timedelta(hours=1)
        dag_id = "test_schedule_dag_fake_scheduled_previous"
        dag = DAG(dag_id=dag_id, schedule_interval=delta, start_date=DEFAULT_DATE)
        dag.add_task(BaseOperator(task_id="faketastic", owner='Also fake', start_date=DEFAULT_DATE))
        dag.create_dagrun(
            run_type=DagRunType.SCHEDULED,
            execution_date=DEFAULT_DATE,
            state=State.SUCCESS,
            external_trigger=True,
        )
        dag.sync_to_db()
        with create_session() as session:
            model = session.query(DagModel).get((dag.dag_id,))
        
        
        assert model.next_dagrun == DEFAULT_DATE
        assert model.next_dagrun_create_after == dag.following_schedule(DEFAULT_DATE)
        self._clean_up(dag_id)
    def test_schedule_dag_once(self):