title: UICollectionView with self-sizing cells resizes cells during insert/remove animation
body: <p>I have a simple UICollectionView with a UICollectionViewFlowLayout that uses autolayout to allow for self-sizing cells. Things work great in a static layout, but when I insert or remove cells, the cells resize to the estimated size:</p>
  
  <pre><code>[self.collectionView performBatchUpdates:^{
      [self.collectionView insertItemsAtIndexPaths:@[indexPath]];
  } completion:nil];
  </code></pre>
  
  <p>Beyond setting the estimated size, like this:</p>
  
  <pre><code>layout.estimatedItemSize = CGSizeMake(88.0, 88.0);
  </code></pre>
  
  <p>I'm not doing anything fancy in the collection view. Everything is set up using storyboards.</p>
  
  <p>How can I avoid this resizing? I'm only targeting iOS 8.0 and up so it should be supported.</p>
  
  <p><img src="https://i.stack.imgur.com/drtZm.gif" alt="example of the problem"></p>