title: AVURLAsset Does Not Work After loadValuesAsynchronously fails
body: <p>I'm having this issue which another user on StackOverflow had (this is the post):</p>
  
  <p>I'm doing the following:</p>
  
  <ul>
  <li>Create a new <code>AVURLAsset</code> with a given URL. That URL points to a video on
  a remote web server. </li>
  <li>Attempt to load the tracks property by calling <code>loadValuesAsynchronously(forKeys:completionHandler:)</code> </li>
  <li>The initial request fails, because no internet connection exists </li>
  <li>I notice that
  the request failed by calling <code>statusOfValue(forKey:error:)</code> </li>
  <li>I then wait
  for the connection to re-appear (using some reachability code). As
  soon as it does, I call
  <code>loadValuesAsynchronously(forKeys:completionHandler:)</code>again. </li>
  </ul>
  
  <p>Here's
     where the problems begin. I would imagine that the <code>AVURLAsset</code> goes ahead
     and attempts to reload the tracks property since it failed
     previously. However, this does not seem to happen.
     <code>statusOfValue(forKey:error:)</code> will still return <code>AVKeyValueStatusFailed</code>,
     although a working internet connection is available and the video is
     playable.</p>
  
  <p>Is there a way to reset the state for this given property and to attempt another load? Is there another way to work around this? Or is the only option to recreate the <code>AVURLAsset</code>?</p>
  
  <p>Thanks!</p>