Disable setxattr calls from quarantine subsystem on Chrome OS.

BUG=733943

Change-Id: I6e743469a8dc91536e180ecf4ff0df0cf427037c
Reviewed-on: https://chromium-review.googlesource.com/c/1380571
Commit-Queue: Will Harris <wfh@chromium.org>
Reviewed-by: Raymes Khoury <raymes@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Thiemo Nagel <tnagel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#617961}