Add scheduler daemon to do scheduled job

In some network environment, networking may not get IP at the first
attempt. Install a scheduler so it can check network status
periodically.

BUG=chromium:624660
TEST=Unplugs ethernet, stop networking, and plugs ethernet back.
     Observer /var/log/scheduler_init at the same time and see it
     restarts networking to bring back network.

Change-Id: I331af39346ef867190157c02631fd22fef2b4447
Reviewed-on: https://chromium-review.googlesource.com/391909
Commit-Ready: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Shyh-In Hwang <josephsih@chromium.org>
6 files changed