s3:rpc_server/witness: add handling of MSG_RPCD_WITNESS_REGISTRATION_UPDATE messages
This implements the server side features for the
'net witness [client-move,...]' commands in the end.
These are administrator driven notifications for the witness client.
RPCD_WITNESS_REGISTRATION_UPDATE_FORCE_RESPONSE and
RPCD_WITNESS_REGISTRATION_UPDATE_FORCE_UNREGISTER will be very useful
for later automated testing.
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Günther Deschner <gd@samba.org>