ip[6]tables: fix incorrect alignment in commands_v_options

CMD_ZERO_NUM is 14, so it has to be defined in position 15 in the
commands_v_options array. This does not manifests easily since
commands from 9 to 14 have a very similar pattern in such array.

Based on this patch: http://patchwork.ozlabs.org/patch/188153/

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>