**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
self,
        content: Any,
        context: Dict,
        jinja_env: Optional[jinja2.Environment] = None,
        seen_oids: Optional[Set] = None,
    ) -> Any:
        """
        Render a templated string. The content can be a collection holding multiple templated strings and will
        be templated recursively.
        :param content: Content to template. Only strings can be templated (may be inside collection).
        :type content: Any
        :param context: Dict with values to apply on templated content
        :type context: dict
        :param jinja_env: Jinja environment. Can be provided to avoid re-creating Jinja environments during
            recursion.
        :type jinja_env: jinja2.Environment
        :param seen_oids: template fields already rendered (to avoid RecursionError on circular dependencies)
        :type seen_oids: set
        :return: Templated content
        """
        if not jinja_env:
            jinja_env = self.get_template_env()