ntp.conf: restrict line must be with IP and not with fqdn

Hi

restrict line with ip do not restrict anything.
http://support.ntp.org/bin/view/Support/AccessRestrictions#Section_6.5.1.2.1.
" You may use either a hostname or IP address on the server line. You must use an IP address on the restrict line. There is no harm in adding the restrictions shown in brackets but keep in mind that if you are accepting time from someone it may be considered courteous to allow them to see a bit of information about their client."

So I've patched the recipe to autogenerate IP from given server name.
Working for ipv4/ipv6 address.