Wait for AJAX requests at the JS level in addition to wait for requests at the middleware level

Hopefully, this can solve transient failures such as
https://gitlab.com/gitlab-org/gitlab-ce/issues/29836.
Signed-off-by: Rémy Coutable <remy@rymai.me>

spec/support/wait_for_requests.rb

+require_relative './wait_for_ajax'
+
 module WaitForRequests
   extend self
+  include WaitForAjax
 
   # This is inspired by http://www.salsify.com/blog/engineering/tearing-capybara-ajax-tests
   def wait_for_requests_complete
     Gitlab::Testing::RequestBlockerMiddleware.block_requests!
     wait_for('pending AJAX requests complete') do
-      Gitlab::Testing::RequestBlockerMiddleware.num_active_requests.zero?
+      Gitlab::Testing::RequestBlockerMiddleware.num_active_requests.zero? &&
+        finished_all_ajax_requests?
     end
   ensure
     Gitlab::Testing::RequestBlockerMiddleware.allow_requests!