iptables: fix the wrong appending of jump verdict after the comment.

Fix wrong appending of jump verdict after the comment

For example:
$ iptables-translate -A INPUT -p tcp -m tcp --sport http -s  192.168.0.0/16 -d 192.168.0.0/16 -j LONGNACCEPT -m comment --comment "foobar"
nft add rule ip filter INPUT ip saddr 192.168.0.0/16 ip daddr 192.168.0.0/16 tcp sport 80 counter comment \"foobar\"jump LONGNACCEPT

Note that even without comment with double-quotes (i.e. --comment
"foobar"), it will add quotes:

$ iptables-translate -A FORWARD -p tcp -m tcp --sport http -s 192.168.0.0/16 -d 192.168.0.0/16 -j DROP -m comment --comment singlecomment
nft add rule ip filter FORWARD ip saddr 192.168.0.0/16 ip daddr 192.168.0.0/16 tcp sport 80 counter comment \"singlecomment\"drop

Attempting to apply the translated/generated rule will result to:

$ nft add rule ip filter INPUT ip saddr 192.168.0.0/16 ip daddr  192.168.0.0/16 tcp sport 80 counter comment \"foobar\"jump LONGNACCEPT
<cmdline>:1:111-114: Error: syntax error, unexpected jump, expecting endof file or newline or semicolon
add rule ip filter INPUT ip saddr 192.168.0.0/16 ip daddr 192.168.0.0/16 tcp sport 80 counter comment "foobar"jump LONGNACCEPT

After this patch
$ iptables-translate -A INPUT -p tcp -m tcp --sport http -s 192.168.0.0/16 -d 192.168.0.0/16 -j LONGNACCEPT -m comment --comment "foobar"
nft add rule ip filter INPUT ip saddr 192.168.0.0/16 ip daddr 192.168.0.0/16 tcp sport 80 counter jump LONGNACCEPT comment \"foobar\"
which is correct translation

Signed-off-by: Shyam Saini <mayhs11saini@gmail.com>
Reviewed-by: Shivani Bhardwaj <shivanib134@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>