title: Remote command seek forward (or backward) does not work
body: <p>I want to be able to seek forward and backward from the lock screen. The code is pretty simple:</p>
  
  <pre><code>MPRemoteCommandCenter *commandCenter = [MPRemoteCommandCenter sharedCommandCenter];
  [commandCenter.seekForwardCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent *event) {
      /// seek forward
      return MPRemoteCommandHandlerStatusSuccess;
  }];
  
  [commandCenter.seekBackwardCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent *event) {
      /// seek backward
      return MPRemoteCommandHandlerStatusSuccess;
  }];
  </code></pre>
  
  <p>However on the lock screen the playback progress view is not seek-able.</p>
  
  <p><a href="https://stackoverflow.com/questions/21041075/how-to-show-seek-track-duration-on-control-center">Here</a> is a similar issue, but I need to use <code>MPRemoteCommandCenter</code> (to disable some of default controls). May be somebody can help us both)</p>