title: supervisord not restarting on HUP signal
body: <pre><code>sudo kill -SIGHUP `cat /var/run/supervisor.pid`
  </code></pre>
  
  <p>causes supervisor to kill it's child processes then itself but it doesn't restart as per the docs. Same behaviour if I call <code>reload</code> from within supervisorctl.</p>
  
  <p>Version: 3.0b1</p>