Add a script to flash firmware by servo automatically

- Start servod.
- Shutdown DUT.
- Flash netboot firmware by servo.
- Boot DUT and check its status.

BUG=chrome-os-partner:12439
TEST=flash netboot firmware and boot to factory image

Change-Id: I7f258e3cfba0d7991b7000fd057cf651fdb35041
Reviewed-on: https://gerrit.chromium.org/gerrit/30176
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Commit-Ready: Shik Chen <shik@chromium.org>
Tested-by: Shik Chen <shik@chromium.org>
1 file changed