fix rclone list without extra ns

rclone.go

@@ -92,8 +92,10 @@ func (rc *RClone) Close() error {
 }
 
 func (rc *RClone) List(ns []string, limits ...string) ([]string, error) {
-	namespace := path.Join(resolveNamespace(ns))
-	namespace = path.Join(rc.ns, namespace)
+	namespace := rc.ns
+	if len(ns) > 0 {
+		namespace = path.Join(rc.ns, resolveNamespace(ns))
+	}
 	limits = resolveLimits(limits)
 
 	f, err := fs.NewFs(namespace)