Fix gometalint errors

Signed-off-by: Manish Tomar <manish.tomar@docker.com>

registry/api/v2/urls.go

@@ -252,15 +252,3 @@ func appendValuesURL(u *url.URL, values ...url.Values) *url.URL {
 	u.RawQuery = merged.Encode()
 	return u
 }
-
-// appendValues appends the parameters to the url. Panics if the string is not
-// a url.
-func appendValues(u string, values ...url.Values) string {
-	up, err := url.Parse(u)
-
-	if err != nil {
-		panic(err) // should never happen
-	}
-
-	return appendValuesURL(up, values...).String()
-}