cmd/godoc: increase test timeout

Darwin was flaking. Its HFS filesystem is probably too slow.

Change-Id: I44ea6de8dae8054d41c94c0c36e703e62fbdfcd9
Reviewed-on: https://go-review.googlesource.com/30954
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

cmd/godoc/godoc_test.go

@@ -140,7 +140,7 @@ func waitForServerReady(t *testing.T, addr string) {
 	waitForServer(t,
 		fmt.Sprintf("http://%v/", addr),
 		"The Go Programming Language",
-		5*time.Second)
+		15*time.Second)
 }
 
 func waitForSearchReady(t *testing.T, addr string) {