pjax: Fix placement of footer

Footer should not be in #pjax_container, because the footer is not rendered
for non PJAX requests.

include/staff/footer.inc.php

+</div>
+</div>
 <?php if (!isset($_SERVER['HTTP_X_PJAX'])) { ?>
-    </div>
     <div id="footer">
         Copyright &copy; 2006-<?php echo date('Y'); ?>&nbsp;<?php echo (string) $ost->company ?: 'osTicket.com'; ?>&nbsp;All Rights Reserved.
     </div>
@@ -13,7 +14,6 @@ if(is_object($thisstaff) && $thisstaff->isStaff()) { ?>
 <?php
 } ?>
 </div>
-</div>
 <div id="overlay"></div>
 <div id="loading">
     <i class="icon-spinner icon-spin icon-3x pull-left icon-light"></i>