title: Remove corner shadow/offset in grouped UITableView
body: <p>When a UITableView of type UITableViewStyleGrouped has a background view that is a non-default color or pattern image on the iPad, the rounded corners have an ugly extra line, sort of like a bevel effect or drop shadow:</p>
  
  <p><img src="https://i.stack.imgur.com/9Wb46.png" alt="ugly table view corners"></p>
  
  <p>Does anyone know of any way to get rid of the extra line at the bottom of the table?</p>