selftests: openvswitch: Test ICMP related matches work with SNAT

Add a test case for regression in openvswitch nat that was fixed by
commit e6345d28 ("netfilter: nf_nat: fix action not being set for
all ct states").

Link: https://lore.kernel.org/netdev/20231221224311.130319-1-brad@faucet.nz/
Link: https://mail.openvswitch.org/pipermail/ovs-dev/2024-January/410476.html


Suggested-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Brad Cowie <brad@faucet.nz>
Tested-by: Aaron Conole <aconole@redhat.com>
Acked-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>