UISearchBar layout inconsistency between iOS 11 and iOS 9.3 - ios

Question

The search bar on iOS 9.3 keeps hiding behind table view although it is part of its header. How can I make it consistent between iOS versions?
One such difference:
on iOS 11
on iOS 9.3
in SelectCountryViewController: UITableViewController, UISearchBarDelegate, UISearchResultsUpdating:
self.tableView.delegate = self;
configureSearchController()
self.automaticallyAdjustsScrollViewInsets = false;
definesPresentationContext = true
let searchButton: UIBarButtonItem = UIBarButtonItem(title: "", style: .plain, target: self, action: #selector(searchButtonAction))
searchButton.image = UIImage(named: "search")
self.navigationItem.rightBarButtonItem = searchButton
refreshController.attributedTitle = NSAttributedString(string: "")
refreshController.addTarget(self, action: #selector(refreshSelector), for: .valueChanged)
tableView.addSubview(refreshController)
func configureSearchController()
{
resultsController.tableView.delegate = self
resultsController.tableView.dataSource = self
self.searchController = UISearchController(searchResultsController: self.resultsController)
//self.tableView.tableHeaderView = self.searchController.searchBar
self.searchController.searchResultsUpdater = self
self.searchController.dimsBackgroundDuringPresentation = false
searchController.searchBar.delegate = self
self.searchController.searchBar.scopeButtonTitles = []
for subView in searchController.searchBar.subviews {
for subViewOne in subView.subviews {
if subViewOne is UITextField {
searchTextField = subViewOne as! UITextField
subViewOne.backgroundColor = UIColor.white
break
}
}
}
self.automaticallyAdjustsScrollViewInsets = false;
extendedLayoutIncludesOpaqueBars = true
definesPresentationContext = true
}
func searchBarShouldBeginEditing(_ searchBar: UISearchBar) -> Bool {
// tableView.setContentOffset(self.navigationItem, animated: true)
searchController.searchBar.barTintColor = UIColor.white
//searchController.searchBar.layer.borderColor = UIColor.white.cgColor
searchTextField.backgroundColor = UIColor.searchBarTextFieldGrey()
return true
}
func searchBarTextDidEndEditing(_ searchBar: UISearchBar) {
self.searchController.searchBar.showsCancelButton = false
// searchController.searchBar.barTintColor = nil
searchTextField.backgroundColor = UIColor.white
searchController.searchBar.barTintColor = nil
}
override func viewWillDisappear(_ animated: Bool) {
self.navigationController?.navigationBar.shadowImage = nil
}
#objc func refreshSelector()
{
if(!searchLoaded)
{
searchLoaded = true
self.tableView.tableHeaderView = searchController.searchBar
print( "Got ya")
self.navigationItem.rightBarButtonItem = nil
}
refreshController.endRefreshing()
}
#objc func searchButtonAction() {
if(!searchLoaded)
{
searchLoaded = true
self.tableView.tableHeaderView = searchController.searchBar
// self.navigationItem.titleView = searchController.searchBar
}
self.searchController.searchBar.becomeFirstResponder()
self.searchController.searchBar.text = ""
self.navigationItem.rightBarButtonItem = nil
}