Add possibility to change addresses where VNC server listens for new
connections. Prior to 6.0 this functionality was available through
'change' qmp command which was deleted.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220401143936.356460-3-vsementsov@openvz.org>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>