title: Airflow None Schedule is not working. Tasks are still running automatically
body: <p>I have an airflow dag which i don't want to schedule. I'm using <code>schedule_interval:None</code> in my dag file but the dag is still running automatically once it is deployed.
  Airflow version used: <code>2.1.0</code></p>
  <p>Airflow Screenshot Attached.
  <a href="https://i.stack.imgur.com/ikEdG.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ikEdG.png" alt="enter image description here" /></a>
  I'm using the following python code in my dag file.</p>
  <pre><code>import os
  import sys
  import logging
  import croniter
  import datetime
  from datetime import timedelta
  from airflow import DAG
  from airflow.operators.python_operator import PythonOperator
  
  
  
  default_args = {
  'owner': 'test-owner',
  'depends_on_past': True,
  'start_date': '2021-11-14',
  'email': ['test.owner@gmail.com'],
  'email_on_failure': True,
  'email_on_retry': True,
  'retries': 1,
  'retry_delay': timedelta(minutes=5),
  'schedule_interval':None,
   }
  
   dag = DAG(
  'test-dag',
  default_args=default_args,
  description='test description'
  )
  
  def test_task(ds, **kwargs):
      print(kwargs)
      print(ds)
  
  
  task = PythonOperator(
      task_id=&quot;test_task&quot;,
      provide_context=True,
      python_callable=test_task,
      op_kwargs={&quot;image&quot;: &quot;value&quot;},
      dag=dag,
  )
  </code></pre>
  <p>Also I have setup airflow env variables to the following:</p>
  <ul>
  <li><code>AIRFLOW__CORE__LOAD_EXAMPLES: &quot;False&quot;</code></li>
  <li><code>AIRFLOW__SCHEDULER__DAG_DIR_LIST_INTERVAL: 30</code></li>
  <li><code>AIRFLOW__CORE__DAGS_ARE_PAUSED_AT_CREATION: &quot;False&quot;</code></li>
  </ul>