DRConnectorClass has a set_configured method, however:
  * There is only one implementation, and only ever likely to be one
  * There's exactly one caller, and that's (now) local
  * The implementation is very straightforward

So abolish the method entirely, and just open-code what we need.
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>
Reviewed-by: NLaurent Vivier <lvivier@redhat.com>
Reviewed-by: NGreg Kurz <groug@kaod.org>
Tested-by: NDaniel Barboza <danielhb@linux.vnet.ibm.com>