socket: Add num connections to qio_net_listener_open_sync()

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
diff --git a/qemu-nbd.c b/qemu-nbd.c
index 0496454..83b6c32 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -1054,7 +1054,7 @@
     server = qio_net_listener_new();
     if (socket_activation == 0) {
         saddr = nbd_build_socket_address(sockpath, bindto, port);
-        if (qio_net_listener_open_sync(server, saddr, &local_err) < 0) {
+        if (qio_net_listener_open_sync(server, saddr, 1, &local_err) < 0) {
             object_unref(OBJECT(server));
             error_report_err(local_err);
             exit(EXIT_FAILURE);