Make end to end specs less brittle

Insert a short sleep while waiting for Ajax to ensure all requests
have finished and the select is done updating.

Author: tf

spec/features/end_to_end_spec.rb

@@ -80,6 +80,7 @@ def select_box_items
 
   def wait_for_ajax
     Timeout.timeout(Capybara.default_max_wait_time) do
+      sleep 0.1
       loop until finished_all_ajax_requests?
     end
   end