**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
CustomOperator(task_id='simple_task', dag=dag, bash_command="true")
        serialized_dag = SerializedDAG.to_dict(dag)
        self.assertIn("bash_command", serialized_dag["dag"]["tasks"][0])
        dag = SerializedDAG.from_dict(serialized_dag)
        simple_task = dag.task_dict["simple_task"]
        self.assertEqual(getattr(simple_task, "bash_command"), "true")
        
        
        
        
        self.assertEqual(
            serialized_dag["dag"]["tasks"][0]["_operator_extra_links"],
            [{'tests.test_utils.mock_operators.CustomOpLink': {}}],
        )
        
        self.assertCountEqual(simple_task.extra_links, ['Google Custom', 'airflow', 'github', 'google'])
        ti = TaskInstance(task=simple_task, execution_date=test_date)
        ti.xcom_push('search_query', "dummy_value_1")
        
        custom_inbuilt_link = simple_task.get_extra_links(test_date, CustomOpLink.name)
        self.assertEqual('http://google.com/custom_base_link?search=dummy_value_1', custom_inbuilt_link)
        
        google_link_from_plugin = simple_task.get_extra_links(test_date, GoogleLink.name)
        self.assertEqual("https://www.google.com", google_link_from_plugin)
    def test_extra_operator_links_logs_error_for_non_registered_extra_links(self):
        """
        Assert OperatorLinks not registered via Plugins and if it is not an inbuilt Operator Link,
        it can still deserialize the DAG (does not error) but just logs an error
        """
        class TaskStateLink(BaseOperatorLink):