**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/baseoperator.py
"""
        Called for [Operator] > [Outlet], so that if other is an attr annotated object
        it is set as an outlet of this Operator.
        """
        if not isinstance(other, Iterable):
            other = [other]
        for obj in other:
            if not attr.has(obj):
                raise TypeError(f"Left hand side ({obj}) is not an outlet")
        self.add_outlets(other)
        return self
    def __lt__(self, other):
        """
        Called for [Inlet] > [Operator] or [Operator] < [Inlet], so that if other is
        an attr annotated object it is set as an inlet to this operator
        """
        if not isinstance(other, Iterable):
            other = [other]
        for obj in other:
            if not attr.has(obj):
                raise TypeError(f"{obj} cannot be an inlet")
        self.add_inlets(other)
        return self
    def __setattr__(self, key, value):