mtpd: add setpriority to seccomp

BUG=chromium:600780
TEST=manually tested as described in the issue

Change-Id: Ifef59fce726af2f72ba5f1e146c0caa69e6ea45a
Reviewed-on: https://chromium-review.googlesource.com/347913
Commit-Ready: Naoki Fukino <fukino@chromium.org>
Tested-by: Naoki Fukino <fukino@chromium.org>
Reviewed-by: David Reveman <reveman@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>
3 files changed