**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
import pendulum
import pytest
from dateutil.relativedelta import relativedelta
from freezegun import freeze_time
from parameterized import parameterized
from airflow import models, settings
from airflow.configuration import conf
from airflow.decorators import task as task_decorator
from airflow.exceptions import AirflowException, DuplicateTaskIdFound
from airflow.models import DAG, DagModel, DagRun, DagTag, TaskFail, TaskInstance as TI
from airflow.models.baseoperator import BaseOperator
from airflow.models.dag import dag as dag_decorator
from airflow.models.dagparam import DagParam
from airflow.operators.bash import BashOperator
from airflow.operators.dummy import DummyOperator
from airflow.operators.subdag import SubDagOperator
from airflow.security import permissions
from airflow.utils import timezone
from airflow.utils.file import list_py_file_paths
from airflow.utils.session import create_session, provide_session
from airflow.utils.state import State
from airflow.utils.timezone import datetime as datetime_tz
from airflow.utils.types import DagRunType
from airflow.utils.weight_rule import WeightRule
from tests.models import DEFAULT_DATE
from tests.test_utils.asserts import assert_queries_count
from tests.test_utils.db import clear_db_dags, clear_db_runs
TEST_DATE = datetime_tz(2015, 1, 2, 0, 0)
class TestDag(unittest.TestCase):
    def setUp(self) -> None: