**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
tests/serialization/test_dag_serialization.py
return dag.following_schedule(execution_date)
    default_args = {'start_date': datetime(2019, 7, 10)}
    dag = DAG(
        'user_defined_macro_filter_dag',
        default_args=default_args,
        user_defined_macros={
            'next_execution_date': compute_next_execution_date,
        },
        user_defined_filters={'hello': lambda name: 'Hello %s' % name},
        catchup=False,
    )
    BashOperator(
        task_id='echo',
        bash_command='echo "{{ next_execution_date(dag, execution_date) }}"',
        dag=dag,
    )
    return {dag.dag_id: dag}
def collect_dags(dag_folder=None):