add ServiceSingleSignOn test link

clientarea.tpl

@@ -9,7 +9,7 @@
         <tr>
           <td colspan=2>
             <button type="button" class="btn btn-default">
-              <a href=/clientarea.php?action=productdetails&id={$serviceid}&dosinglesignon=1 target=_blank>Einloggen</a>
+              <a href=/whmcs/clientarea.php?action=productdetails&id={$serviceid}&dosinglesignon=1 target=_blank>Einloggen</a>
             </button>
           </td>
         </tr>