title: airflow: 1.7: DAG not being updated in GUI
body: <p>I have my dag file <code>test1.py</code> defined under <code>/opt/airflow/dags</code> directory. Initially, the file has only one task, <code>test1_task01</code>. In my GUI, the dag shows up correctly with only one task. However, when I add another task to my DAG that looks like: </p>
  
  <pre><code>DAG - test1_task01 &lt;- test2_task01 (representative - not airflow syntax)
  </code></pre>
  
  <p>I do not see the updated DAG in my GUI. The GUI still has the old DAG. <code>airflow list_tasks &lt;dagname&gt;</code> shows the correct DAG relationships and <code>airflow scheduler</code> executes the latest version, but the GUI somehow is not pulling the latest info. </p>
  
  <p>How do I get an updated view of my DAGs via the GUI?</p>