title: UISearchController disable cancel UIBarButtonItem
body: <h1>The Problem</h1>
  <p>I am trying to use UISearchController to search for a destination on a map view. I want the UISearchBar to appear in the navigation bar, but I can't seem to make it do so without it showing a cancel button to the right of it:</p>
  <p><img src="https://i.stack.imgur.com/wBObM.png" alt="enter image description here" /></p>
  <p>This Cancel button has disappeared at times, whilst I'm playing around, but I can't get it to not appear now I have got the search table showing how I want it to:</p>
  <p><img src="https://i.stack.imgur.com/2odTj.png" alt="enter image description here" /></p>
  <p>I'm sure there must be something small I'm doing ever so slightly wrong, but I can't work out what it is...</p>
  <h1>My Code</h1>
  <pre><code>self.resultsViewController = [UITableViewController new];
  self.searchController = [[UISearchController alloc] initWithSearchResultsController:self.resultsViewController];
  self.searchController.searchResultsUpdater = self;
  self.searchController.hidesNavigationBarDuringPresentation = false;
  self.searchController.delegate = self;
  self.searchBar = self.searchController.searchBar;
  self.searchBar.placeholder = self.stage.title;
  self.searchBar.searchBarStyle = UISearchBarStyleMinimal;
  
  self.definesPresentationContext = true;
  self.navigationItem.titleView = self.searchBar;
  
  self.resultsTableView = self.resultsViewController.tableView;
  self.resultsTableView.dataSource = self;
  self.resultsTableView.delegate = self;
  </code></pre>