title: Airflow worker trying to connect to redis despite rabbitmq configuration
body: <p>I installed and set up Airflow 2.0.1 with Celery, Rabbitmq and Postgresql9.6 on RHEL7, using the constraints <a href="https://raw.githubusercontent.com/apache/airflow/constraints-2.0.1/constraints-3.7.txt" rel="nofollow noreferrer">https://raw.githubusercontent.com/apache/airflow/constraints-2.0.1/constraints-3.7.txt</a>.
  So I am not using Docker container, and in fact am building a cluster with 3 nodes.</p>
  <p>I created DB and username for PSQL, and created user and set permission for Rabbitmq and am able to access its WebUI in 15672 port.
  I am able to run airflow webserver and scheduler and access airflow WebUI with no problem.</p>
  <p>The issue arises when I try to start airflow worker (whether from master node or worker nodes). Even though airflow.cfg is set to point out to rabbitmq, I get the error that says:</p>
  <pre><code>ImportError: Missing redis library (pip install redis)
  </code></pre>
  <p>Because it is trying to access redis instead of rabbitmq, but I have no idea why.</p>
  <p>I checked airflow.cfg line by line and there is not a single line with redis, so am I missing a configuration or what?</p>
  <p>My airflow.cfg configuration:</p>
  <pre><code>sql_alchemy_conn = postgresql+psycopg2://airflow_user:airflow_pw@10.200.159.59:5432/airflow
  broker_url= amqp://rabbitmq_user:rabbitmq_pw@10.200.159.59:5672/airflow_virtual_host
  celery_result_backend = db+postgresql://airflow_user:airflow_pw@10.200.159.59:5432/airflow
  
  dags_are_paused_at_creation = True
  load_examples = False
  </code></pre>
  <p>Why does my airflow worker try to reach redis when it is configured for rabbitmq?</p>