payload: don't remove icmp family dependency in special cases

payload: don't remove icmp family dependency in special cases

When using nftables to filter icmp-in-ipv6 or icmpv6-in-ipv4 we
erronously removed the dependency, i.e. "lis ruleset" shows

table ip6 filter { chain output {
		type filter hook output priority 0; policy accept;
		icmp type destination-unreachable
} }

but that won't restore because of ip vs ipv6 conflict.

After this patch, this lists as

 meta l4proto icmp icmp type destination-unreachable

instead.  We still remove the dependency in "ip" family.

Same applies to icmpv6-in-ip.

Reported-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>