unix: fix TestGetfsstat the same way as CL 28550 in pkg syscall
unix: fix TestGetfsstat the same way as CL 28550 in pkg syscall

Same as https://golang.org/cl/28550 but for x/sys/unix.

Updates golang/go#16937

Change-Id: Ie93df8ff1c40a7f2d98f1fb3ecf6110330bf1cbc
Reviewed-on: https://go-review.googlesource.com/28585
Reviewed-by: Josh Bleecher Snyder <cdc248cc4d32e4fbfe04e45228163bcecd48a0b9@gmail.com>
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/sys,multiplay/golang-sys,golang/sys,multiplay/golang-sys,multiplay/golang-sys,multiplay/golang-sys,golang/sys