(legacy) missing dependency in services_opendns.php

src/www/services_opendns.php

@@ -31,6 +31,7 @@ require_once("guiconfig.inc");
 require_once("system.inc");
 require_once("pfsense-utils.inc");
 require_once("services.inc");
+require_once("interfaces.inc");
 
 if (!is_array($config['opendns'])) {
 	$config['opendns'] = array();