Bug 33263: Fix random failure in patrons_search.t

There is a missing wait_for_ajax. After we click "next", we need to make
sure we are using the correct response.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit e81e2c9ed5)
Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>

t/db_dependent/selenium/patrons_search.t

@@ -300,6 +300,7 @@ subtest 'Search patrons' => sub {
         is( $patron_selected_text, "Patrons selected: 2", "Two patrons are selected" );
 
         $driver->find_element('//*[@id="memberresultst_next"]')->click;
+        $s->wait_for_ajax;
         @checkboxes = $driver->find_elements(
             '//input[@type="checkbox"][@name="borrowernumber"]');
         $checkboxes[0]->click;