title: Can't edit UISearchController UISearchBar in navigationItem titleView
body: <p>When setting a UISearchController search bar in the navigationItem titleView, the search bar can't be edited.</p>
  
  <p>In my viewDidLoad I am configuring a UISearchController.</p>
  
  <pre><code>self.searchViewController = [self.storyboard instantiateViewControllerWithIdentifier:NSStringFromClass([SearchViewController class])];
  self.searchViewController.delegate = self;
  self.searchController = [[UISearchController alloc] initWithSearchResultsController:self.searchViewController];
  self.searchController.delegate = self;
  self.searchController.searchResultsUpdater = self;
  self.searchController.searchBar.delegate = self;
  self.navigationItem.titleView = self.searchController.searchBar;
  </code></pre>
  
  <p>I can't tap the search bar. The cursor does not appear and there is no user interaction.</p>
  
  <p>Oddly, if I initialize the UISearchController locally without setting it to a property, then I can edit the search bar, just no delegate callbacks.</p>
  
  <pre><code>self.searchViewController = [self.storyboard instantiateViewControllerWithIdentifier:NSStringFromClass([SearchViewController class])];
  self.searchViewController.delegate = self;
  UISearchController *searchController = [[UISearchController alloc] initWithSearchResultsController:self.searchViewController];
  searchController.delegate = self;
  searchController.searchResultsUpdater = self;
  searchController.searchBar.delegate = self;
  self.navigationItem.titleView = searchController.searchBar;
  </code></pre>
  
  <p>Another interesting behavior is that the clear button works (if some text is set in the search bar while initializing).</p>