title: Firestore listener initialized with LifeCycleOwner argument misses updates when activity is paused
body: <p>In my app I'm using a Firestore listener to listen for changes to a certain document. I init this listener using a LifeCycleOwner argument:</p>
  
  <pre><code>FireUtil.Events.getEvent( mEventKey ).addSnapshotListener( EventMainActivity.this, (documentSnapshot, e)
  </code></pre>
  
  <p>When I make change to this document in another activity (the one in which I added the listener is paused), and return to the initial activity, changes are not visible (a restart of the activity is required).</p>
  
  <p>When I remove the life-cycle owner argument, the listener is triggered and changes are visible (but I need to manually clean the listener).</p>
  
  <p>Is this intended behavior, or am I missing something?</p>