net/virtio: return early when failover primary alread added

Bail out when primary device was already added before.
This avoids printing a wrong warning message during reboot.

Fixes: 9711cd0 ("net/virtio: add failover support")
Signed-off-by: Jens Freimann <jfreimann@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

hw/net/virtio-net.c

@@ -759,6 +759,10 @@ static void failover_add_primary(VirtIONet *n, Error **errp)
 {
     Error *err = NULL;
 
+    if (n->primary_dev) {
+        return;
+    }
+
     n->primary_device_opts = qemu_opts_find(qemu_find_opts("device"),
             n->primary_device_id);
     if (n->primary_device_opts) {