transporthandler: Support Gateway MAC

Adds support for setting the MAC address of the gateway. Most of the
interesting code in this change is around saving / restoring the gateway
MAC address when the gateway or interface change.

Change-Id: I85b7c665c44af4f030f51456be355f3eb11ab2fc
Signed-off-by: William A. Kennington III <wak@google.com>
1 file changed