title: UICollectionView rotation animation
body: <p>I have two different UIViewControllers, and both of them have UiCollectionView.
  Problems appears when I try rotate iPad.
  Next I have in portrait position</p>
  
  <p><img src="https://i.stack.imgur.com/9yHS2.png" alt="enter image description here"></p>
  
  <p>When I rotate to landscape I reload my collectionView, so in lanscape mode I need have 3 columns</p>
  
  <pre><code>- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
  {
      [self.collectionView reloadData];
  }
  </code></pre>
  
  <p>In first viewController all good, and when collectionView begin rotate controller still have 3 columns</p>
  
  <p><img src="https://i.stack.imgur.com/pc7Xs.png" alt="enter image description here"></p>
  
  <p>But when I try do it in another controller, I get bad situation</p>
  
  <p><img src="https://i.stack.imgur.com/LzbAt.png" alt="enter image description here"></p>
  
  <p>It is looks like in one moment two collectionView in my view, and then one of them is disappearing.</p>
  
  <p>I use standart UICollectionViewFlowLayout and have same methods for buils layout</p>