lintapp: fix build failure

Previously lintapp would fail with httputil.Transport is not defined.
It seems like this was moved to become an AuthTransport, so let's use
that instead.

Change-Id: I4fc3006a352ed1ae419063ca2c4cc9b35cb8b8a3
Reviewed-on: https://go-review.googlesource.com/38168
Reviewed-by: Tuo Shan <shantuo@google.com>
diff --git a/lintapp/main.go b/lintapp/main.go
index 7f184f8..4bcf7db 100644
--- a/lintapp/main.go
+++ b/lintapp/main.go
@@ -113,11 +113,11 @@
 func httpClient(r *http.Request) *http.Client {
 	c := appengine.NewContext(r)
 	return &http.Client{
-		Transport: &httputil.Transport{
+		Transport: &httputil.AuthTransport{
 			Token:        github.Token,
 			ClientID:     github.ClientID,
 			ClientSecret: github.ClientSecret,
-			Base:         &urlfetch.Transport{Context: c, Deadline: 10 * time.Second},
+			Base:         &urlfetch.Transport{Context: c},
 			UserAgent:    fmt.Sprintf("%s (+http://%s/-/bot)", appengine.AppID(c), r.Host),
 		},
 	}