CHROMIUMOS: autotest: add /dev/watchdog kernel test

If a HW watchdog is present, verify that opening but NOT petting
the watchdog results in a reset.

BUG=chromium-os:36756
TEST=verify test behaves as expected on lucas, lumpy, alex platforms

Change-Id: I8ea8ea2dd99e90c9591baf2724d36106545c6a98
Signed-off-by: Grant Grundler <grundler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39555
Reviewed-by: Scott Zawalski <scottz@chromium.org>
2 files changed