The test TestACL failed when ran on a Windows set
up in another language as the "Guest" account
name is translated. The SID of the group of Guests
always exist and is used instead.

Fixes #26658

Change-Id: Ia885d08a9e50563787e389c2d2dc2547881a2943
Reviewed-on: https://go-review.googlesource.com/126598Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>