virtio-net: fix data corruption with OOM

virtio-net: fix data corruption with OOM

virtio net used to unlink skbs from send queues on error,
but ever since e93d646a6c3ef84a9b1081139aac6be48c4f581c
we do not do this. This causes guest data corruption and crashes
with vhost since net core can requeue the skb or free it without
it being taken off the list.

This patch fixes this by queueing the skb after successful
transmit.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>