title: TVCardView rounded corners strange behaviour
body: <p>I'm setting up a new tvOS app with a <code>UISplitViewController</code> and a <code>UICollectionView</code> as a detail view. To achieve some nice out-of-the-box focus behaviour, I'm trying to use <code>TVCardView</code> inside the <code>UICollectionViewCell</code> and adding an image view and a label to the card views content view (in interface builder). That works, but the problem is that the card views always applies rounded corners to the content once they have been selected. Initially all views have sharp corners, but as soon as a cell has been selected, it switches to rounded corners.
  First of all, I don't even want rounded corners and in Apples examples, I never see those rounded corners anyway: <a href="https://developer.apple.com/documentation/tvuikit/tvcardview" rel="nofollow noreferrer">https://developer.apple.com/documentation/tvuikit/tvcardview</a>
  But even then, it's kind of useless to have rounded corners only partially after selection.</p>
  <p>Has anyone experience with <code>TVCardView</code> and knows about this strange behaviour? I cannot find any example code or more detailed documentation. I also tried to use <code>TVLockupView</code> instead, but that doesn't seem to be supported by interface builder.</p>