Avoid using "example.com" in integration test

This test appears to trigger HTTP requests to "example.com", which may
explain why it is not behaving consistently. This changes it to use an
internal HTTP server to avoid unexpected behavior caused by firewalls or
proxies.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
Upstream-commit: b483e4f09c128c2fabf82f787c0cf737c17c9c10
Component: engine

components/engine/integration-cli/docker_api_images_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"encoding/json"
 	"net/http"
+	"net/http/httptest"
 	"net/url"
 	"strings"
 
@@ -120,13 +121,16 @@ func (s *DockerSuite) TestAPIImagesHistory(c *check.C) {
 func (s *DockerSuite) TestAPIImagesImportBadSrc(c *check.C) {
 	testRequires(c, Network)
 
+	server := httptest.NewServer(http.NewServeMux())
+	defer server.Close()
+
 	tt := []struct {
 		statusExp int
 		fromSrc   string
 	}{
-		{http.StatusNotFound, "http://example.com/nofile.tar"},
-		{http.StatusNotFound, "example.com/nofile.tar"},
-		{http.StatusNotFound, "example.com%2Fdata%2Ffile.tar"},
+		{http.StatusNotFound, server.URL + "/nofile.tar"},
+		{http.StatusNotFound, strings.TrimPrefix(server.URL, "http://") + "/nofile.tar"},
+		{http.StatusNotFound, strings.TrimPrefix(server.URL, "http://") + "%2Fdata%2Ffile.tar"},
 		{http.StatusInternalServerError, "%2Fdata%2Ffile.tar"},
 	}