libxt_cluster: fix inversion in the cluster match

libxt_cluster: fix inversion in the cluster match

In libxt_cluster.c, we use:

info->flags |= (1 << XT_CLUSTER_F_INV);

but we should use instead:

info->flags |= XT_CLUSTER_F_INV;

since the definition of XT_CLUSTER_F_INV is:

enum xt_cluster_flags {
        XT_CLUSTER_F_INV        = (1 << 0)
};

This fixes the inversion in the cluster match.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>