iptables-restore: resolve confusing policy error message

iptables-restore: resolve confusing policy error message

When iptables-restore (and ip6tables-restore) is unable to set a
chain's policy, it responds with a confusing message, e.g.:

iptables-restore v1.4.9: Can't set policy "PREROUTING" on "ACCEPT"
line 16: Bad built-in chain name

This is due to the chain and policy arguments being used in the wrong
order. The attached patch corrects this problem.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>