After unreverting the linkstate change patch, hook up notification handlers that didn't exist when the first patch was created, like EthernetDataTracker.java and Vpn.java. For the observers that handle interfaceStatusChanged(), I made interfaceLinkStatusChanged() call it so they both do the same thing. Change-Id: I0077e5e5f48f3932ba98f5bf363243892f2de6cc Signed-off-by: Mike J. Chen <mjchen@google.com>