extensions: libxt_NFLOG: Add group_info and remove multiple keywords

extensions: libxt_NFLOG: Add group_info and remove multiple keywords

Add group_info with every rule as it is mandatory to consider logging to
be same type as NFLOG.
Remove multiple log keywords to avoid loading multiple log expressions
at a time.

Examples:

$ sudo iptables-translate -I INPUT -j NFLOG --nflog-threshold 2
nft insert rule ip filter INPUT counter log queue-threshold 2 group 0

$ sudo iptables-translate -A FORWARD -j NFLOG --nflog-group 32 --nflog-prefix "Prefix 1.0"
nft add rule ip filter FORWARD counter log prefix \"Prefix 1.0\" group 32

Reported-by: Arturo Borrero <arturoborreroglez@gmail.com>
Signed-off-by: Shivani Bhardwaj <shivanib134@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>