iptables: add ipset support for centos
iptables: define do_ipset/iptables
iptables: add option not[source|...]
iptables: fix version check, use list both
iptables: refactor rules check
nginx: add option nginx.pkg_installed
hostname: add support for centos 7
rsyncd: no /etc/init.d/rsyncd for centos 6
centos: update rc.local/selinux
rsyncd: update os filter for centos/ubuntu