The overall time package tests increase from 3.85s to 4.85s on my laptop.
But they should be less flaky, and the time is spent sleeping, so it won't
slow down the overall machine running multiple package tests in
parallel.
For #66322.
Change-Id: I66d6647c389c943b53045e8836ede4ba3d4670c7
Reviewed-on: https://go-review.googlesource.com/c/go/+/581315
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com>