Track link status in Ethernet and register service

Add link status tracking (and setting IFF_UP) to ethernet devices.
When the interface is running, register a service with the manager.

BUG=chromium-os:12933
TEST=Manual -- unit tests and plug/unplug ethernet USB and RJ45 sides.

Change-Id: I1233ce5a63efddb7606183dc4daad4d2624d864a
Reviewed-on: http://gerrit.chromium.org/gerrit/1196
Tested-by: Paul Stewart <pstew@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
16 files changed