Followup to https://go-review.googlesource.com/3910

We only need 1000 iteratinons.

Change-Id: Ib63ae53105176abec77bad9609d638aeda7bcd61
Reviewed-on: https://go-review.googlesource.com/3901Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>