A notetsleepg may get stuck if its timeout callback gets invoked
exactly on its deadline due to low precision of nanotime. This change
fixes the comparison so it also resolves the note if the timestamps are
equal.

Updates #28975

Change-Id: I045d2f48b7f41cea0caec19b56876e9de01dcd6c
Reviewed-on: https://go-review.googlesource.com/c/153558
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>