autotest: Add simple test to verify operation of dual radio router

This will assist us in bringing up multi-radio routers quickly.

TEST=suite wifi_matfunc passes with these changes to
site_linux_system.py
BUG=chromium:313963
Change-Id: Id4fa86b9df0d3ba68c9fed2e546e894ddd84aee0
Reviewed-on: https://chromium-review.googlesource.com/176117
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
3 files changed