Fix format call in tests

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

config/setup/basicauth_test.go

@@ -40,7 +40,7 @@ md5:$apr1$l42y8rex$pOA2VJ0x/0TwaFeAF9nX61`
 	var skipHtpassword bool
 	htfh, err := ioutil.TempFile("", "basicauth-")
 	if err != nil {
-		t.Logf("Error creating temp file (%v), will skip htpassword test")
+		t.Logf("Error creating temp file (%v), will skip htpassword test", err)
 		skipHtpassword = true
 	} else {
 		if _, err = htfh.Write([]byte(htpasswdFile)); err != nil {