servod: add connectivity test for atmega

Connect to atmega KB emulator and validate that it's responsive,
and ensure that it is reset on startup.

BUG=chromium:502016
TEST=manual, run with atmega, without, observe fail

Change-Id: I6d5b2c5f43f0c2592634ff5f11c2b6ec04ea06f5
Reviewed-on: https://chromium-review.googlesource.com/311810
Commit-Ready: Nick Sanders <nsanders@chromium.org>
Tested-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: danny chan <dchan@chromium.org>
2 files changed