**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
callback = callback_requests.DagCallbackRequest(
                    full_filepath=dag.fileloc,
                    dag_id=self.dag_id,
                    execution_date=self.execution_date,
                    is_failure_callback=False,
                    msg='success',
                )
        
        elif unfinished_tasks and none_depends_on_past and none_task_concurrency and not are_runnable_tasks:
            self.log.error('Deadlock; marking run %s failed', self)
            self.set_state(State.FAILED)
            if execute_callbacks:
                dag.handle_callback(self, success=False, reason='all_tasks_deadlocked', session=session)
            else:
                callback = callback_requests.DagCallbackRequest(
                    full_filepath=dag.fileloc,
                    dag_id=self.dag_id,
                    execution_date=self.execution_date,
                    is_failure_callback=True,
                    msg='all_tasks_deadlocked',
                )
        
        else:
            self.set_state(State.RUNNING)
        self._emit_true_scheduling_delay_stats_for_finished_state(finished_tasks)
        self._emit_duration_stats_for_finished_state()
        session.merge(self)
        return schedulable_tis, callback
    @provide_session
    def task_instance_scheduling_decisions(self, session: Session = None) -> TISchedulingDecision: