net: fix qemu_announce_self not emitting packets

commit fefe2a78 accidently dropped the code path for injecting
raw packets. This feature is needed for sending gratuitous ARPs
after an incoming migration has completed. The result is increased
network downtime for vservers where the network card is not virtio-net
with the VIRTIO_NET_F_GUEST_ANNOUNCE feature.

Fixes: fefe2a78
Cc: qemu-stable@nongnu.org
Cc: hongyang.yang@easystack.cn
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Jason Wang <jasowang@redhat.com>