Add a route backwards from the DUT to the test host

This is useful during VPN tests where the default route gets set.

BUG=chromium-os:13757
TEST=Manual: Inspected "ip" commands from debug log.  Thutt: Please
verify

Change-Id: Ib3c86243a6b13c95706b58549049b00df633c348

R=thutt@chromium.org

Review URL: http://codereview.chromium.org/6689026
2 files changed