CHROMIUM: adjust /dev/pts mount settings

Set ptmxmode to match what we use in platform2/init/ today, and to
allow possibly deleting /dev/ptmx in the future.

BUG=chromium:1063545
TEST=CQ passes

Change-Id: Iaa2906d04571f050ce4c0531e75664b7098f4dc5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/upstart/+/3706786
Reviewed-by: Allen Webb <allenwebb@google.com>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
1 file changed