godoc: fix error with gcsBaseURL not being defined

Change-Id: I508209c3bad67b791ee8c162bd4df448f9b84bef
Reviewed-on: https://go-review.googlesource.com/68270
Reviewed-by: Chris Broadfoot <cbro@golang.org>

godoc/dl/dl.go

@@ -424,7 +424,7 @@ func getHandler(w http.ResponseWriter, r *http.Request) {
 		http.NotFound(w, r)
 		return
 	}
-	http.Redirect(w, r, gcsBaseURL+name, http.StatusFound)
+	http.Redirect(w, r, edgeCacheBaseURL+name, http.StatusFound)
 }
 
 func validUser(user string) bool {