title: White line under UINavigationBar in IOS 7
body: <p>I have a <code>UITableViewController</code> with a <code>UISearchDisplayController</code> and <code>UISearchBar</code>.  I'm seeing a white line under the navbar when I present the view in a <code>UITabBarController</code>.  When I present the view modally in a <code>UINavigationController</code>, the line is either gray or black (I can't tell) and it looks perfectly normal.  Any ideas?</p>
  
  <p><img src="https://i.stack.imgur.com/5xWck.png" alt="enter image description here"></p>