While fixing some failing tests, CL 114416 also picked up the newly
added TestXattr from golang.org/x/sys/unix which fails on android. Pick
up CL 114535 to fix it as well.

Also pick up CL 114616 to fix TestStatx occasionally failing on linux.

Change-Id: I6ebebd7761fa7a086d96ee0447dbbc5c6b94131d
Reviewed-on: https://go-review.googlesource.com/114575
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>