fix(api): , _ removed to simplify code in range

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)

api.go

@@ -1094,7 +1094,7 @@ func ServeFd(addr string, handle http.Handler) error {
 
 	// Since ListenFD will return one or more sockets we have
 	// to create a go func to spawn off multiple serves
-	for i, _ := range ls {
+	for i := range ls {
 		listener := ls[i]
 		go func() {
 			httpSrv := http.Server{Handler: handle}