os/user: use correct size for initial call in retryWithBuffer
We were accidentally using the sysconf parameter constant.
Change to using the value of that sysconf parameter.
Change-Id: Id7668e7cced0ce7504df99dbbff0757d29dee8c8
Reviewed-on: https://go-review.googlesource.com/c/go/+/524555
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com> Reviewed-by: Russ Cox <rsc@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com>