igmp: Avoid zero delay when receiving odd mixture of IGMP queries

Commit 5b7c84066733c5dfb0e4016d939757b38de189e4 ('ipv4: correct IGMP
behavior on v3 query during v2-compatibility mode') added yet another
case for query parsing, which can result in max_delay = 0.  Substitute
a value of 1, as in the usual v3 case.

Reported-by: Simon McVittie <smcv@debian.org>
References: http://bugs.debian.org/654876
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
static struct ip_mc_list *igmp_mc_get_idx(struct seq_file *seq, loff_t pos)
{
	struct ip_mc_list *im = igmp_mc_get_first(seq);
	if (im)
		while (pos && (im = igmp_mc_get_next(seq, im)) != NULL)
			--pos;
	return pos ? NULL : im;
}

static struct ip_mc_list *igmp_mc_get_idx(struct seq_file *seq, loff_t pos)
{
	struct ip_mc_list *im = igmp_mc_get_first(seq);
	if (im)
		while (pos && (im = igmp_mc_get_next(seq, im)) != NULL)
			--pos;
	return pos ? NULL : im;
}
