**Apache Airflow version**:
v2.0.0

**What happened**:

Custom operators inheriting from DummyOperator are go in to a scheduled state, where as DummyOperator itself is set straight to success.

**What you expected to happen**:

All operators should be successfully executed.

**How to reproduce it**:

```py
from datetime import datetime
from airflow import DAG
from airflow.operators.dummy_operator import DummyOperator

class MyJob(DummyOperator):
    template_fields_renderers = {
        "body": "json"
    }
    template_fields = ("body",)

    def __init__(self, body, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.body = body

with DAG(
    dag_id="test",
    schedule_interval=None,
    start_date=datetime(2020, 8, 13),
) as dag:
    MyJob(task_id="aaaa", body={"aaa": "bbb"})

```

**Anything else we need to know**:
This is a known problem that we will fix, see: https://github.com/apache/airflow/pull/10956#discussion_r502492775
airflow/models/dagrun.py
return self.run_type == DagRunType.BACKFILL_JOB
    @classmethod
    @provide_session
    def get_latest_runs(cls, session=None):
        """Returns the latest DagRun for each DAG"""
        subquery = (
            session.query(cls.dag_id, func.max(cls.execution_date).label('execution_date'))
            .group_by(cls.dag_id)
            .subquery()
        )
        dagruns = (
            session.query(cls)
            .join(
                subquery,
                and_(cls.dag_id == subquery.c.dag_id, cls.execution_date == subquery.c.execution_date),
            )
            .all()
        )
        return dagruns
    @provide_session
    def schedule_tis(self, schedulable_tis: Iterable[TI], session: Session = None) -> int: