minifirewall_status returns "started" on stdout and exit code 0,
or "stopped" on stdout and exit code 1. The state of minifirewall
is determined by looking for common iptables rules applied by
check_minifirewall is an NRPE plugin for minifirewall. It returns:
* 0 (OK) if the firewall state is consistent with its configuration
(from the alert5 script)
* 1 (WARNING) if the firewall is started but alert5 is not configured
* 2 (CRITICAL) if the firewall is not running but it should be.