Make the updateIssueFrom(url) function return the XMLHttpRequest object (#20180).

Patch by Vincent Robert.

git-svn-id: http://svn.redmine.org/redmine/trunk@14372 e93f8b46-1217-0410-a6f0-8f06a7374b81

public/javascripts/application.js

   $('#all_attributes input, #all_attributes textarea, #all_attributes select').each(function(){
     $(this).data('valuebeforeupdate', $(this).val());
   });
-  $.ajax({
+  return $.ajax({
     url: url,
     type: 'post',
     data: $('#issue-form').serialize()