**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/operators/dummy_operator.py
#
#
#
from airflow.models import BaseOperator
from airflow.utils.decorators import apply_defaults
class DummyOperator(BaseOperator):
    """
    Operator that does literally nothing. It can be used to group tasks in a
    DAG.
    The task is evaluated by the scheduler but never processed by the executor.
    """
    ui_color = '#e8f7e4'
    @apply_defaults
    def __init__(self, **kwargs) -> None:
        super().__init__(**kwargs)
    def execute(self, context):
        pass