title: Android, network request, cancel within onStop but keep on rotation
body: <p>I have a Login Activity. User sends request with email and password to login.
  I'm using Retrofit 2, and there is new functionality to cancel request. (This is not really matter, question is more general).</p>
  
  <p>If user presses back - I want to cancel request. But if user rotate phone - I want request to proceed.
  So I can't call canceling within onStop.
  Of course I can cancel request on Back pressed. But I think there are more cases, when Activity stopped. </p>
  
  <p>Another way I see is to use <code>android:configChanges="orientation"</code>.</p>
  
  <p>I'll be thankful for any ideas and "best practices".</p>