reneg-sec also valid for server_user

src/www/vpn_openvpn_server.php

@@ -1532,7 +1532,7 @@ endif; ?>
                         </div>
                       </td>
                     </tr>
-                    <tr class="opt_mode opt_mode_server_tls_user">
+                    <tr class="opt_mode opt_mode_server_tls_user opt_mode_server_user">
                       <td><a id="help_for_reneg-sec" href="#" class="showhelp"><i class="fa fa-info-circle"></i></a> <?=gettext("Renegotiate time"); ?></td>
                       <td>
                         <input type="text" name="reneg-sec" value="<?=$pconfig['reneg-sec'];?>">