**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
"""Performs dry run for the operator - just render template fields."""
        self.log.info('Dry run')
        for field in self.template_fields:
            content = getattr(self, field)
            if content and isinstance(content, str):
                self.log.info('Rendering template for %s', field)
                self.log.info(content)
    def get_direct_relative_ids(self, upstream: bool = False) -> Set[str]:
        """
        Get set of the direct relative ids to the current task, upstream or
        downstream.
        """
        if upstream:
            return self._upstream_task_ids
        else:
            return self._downstream_task_ids
    def get_direct_relatives(self, upstream: bool = False) -> List["BaseOperator"]: