[NETFILTER]: fix list traversal order in ctnetlink

Currently conntracks are inserted after the head. That means that
conntracks are sorted from the biggest to the smallest id. This happens
because we use list_prepend (list_add) instead list_add_tail. This can
result in problems during the list iteration.

                 list_for_each(i, &ip_conntrack_hash[cb->args[0]]) {
                         h = (struct ip_conntrack_tuple_hash *) i;
                         if (DIRECTION(h) != IP_CT_DIR_ORIGINAL)
                                 continue;
                         ct = tuplehash_to_ctrack(h);
                         if (ct->id <= *id)
                                 continue;

In that case just the first conntrack in the bucket will be dumped. To
fix this, we iterate the list from the tail to the head via
list_for_each_prev. Same thing for the list of expectations.

Signed-off-by: Pablo Neira Ayuso <pablo@eurodev.net>
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>