driver/NameOwnerChanged: refactor to make the handler in line with Name{Lost,Acquired}
driver/NameOwnerChanged: refactor to make the handler in line with Name{Lost,Acquired}

Let the caller generate (if necessary) the strings of the payload.

Signed-off-by: Tom Gundersen <7c8224529a7c718e876cb2496c973509fde1e50e@jklm.no>

bus1/dbus-broker