**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. 

airflow/models/dag.py
If the dag exists already, this flag will be ignored. If this optional parameter
        is not specified, the global config setting will be used.
    :type is_paused_upon_creation: bool or None
    :param jinja_environment_kwargs: additional configuration options to be passed to Jinja
        ``Environment`` for template rendering
        **Example**: to avoid Jinja from removing a trailing newline from template strings ::
            DAG(dag_id='my-dag',
                jinja_environment_kwargs={
                    'keep_trailing_newline': True,
                    # some other jinja2 Environment options here
                }
            )
        **See**: `Jinja Environment documentation
        <https://jinja.palletsprojects.com/en/master/api/#jinja2.Environment>`_
    :type jinja_environment_kwargs: dict
    :param tags: List of tags to help filtering DAGS in the UI.
    :type tags: List[str]
    """
    _comps = {
        'dag_id',
        'task_ids',
        'parent_dag',
        'start_date',
        'schedule_interval',
        'full_filepath',
        'template_searchpath',
        'last_loaded',
    }
    __serialized_fields: Optional[FrozenSet[str]] = None
    def __init__(