virtio-net: drop assert on vm stop

On vm stop, vm_running state set to stopped
before device is notified, so callbacks can get envoked with
vm_running = false; and this is not an error.

Cc: [email protected]
Acked-by: Jason Wang <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
(cherry picked from commit 131c522)
Signed-off-by: Michael Roth <[email protected]>

Author: mstsirkin

hw/net/virtio-net.c

@@ -1125,8 +1125,6 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
         return num_packets;
     }
 
-    assert(vdev->vm_running);
-
     if (q->async_tx.elem.out_num) {
         virtio_queue_set_notification(q->tx_vq, 0);
         return num_packets;