qemu: Emit NIC_MAC_CHANGE event

qemu: Emit NIC_MAC_CHANGE event

So far, we only process NIC_RX_FILTER_CHANGED event when the
corresponding device has 'trustGuestRxFilters' enabled. And the
event is emitted only for virtio model. IOW, this is fairly
limited situation and other scenarios don't emit any event (e.g.
change of MAC address on a PCI passthrough device).

Resolves: https://issues.redhat.com/browse/RHEL-7035
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>