Fixes #66

By default, a Null value keeps the variable current value as-is.
Set an Array (can be empty) to replace the value.

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
minifirewall.

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
properly
* 2 (CRITICAL) if the firewall is not running but it should be.

Debian migrated its security.debian.org repository to Fastly CDN
(security-cdn.debian.org) so we have to whitelist it too to make
security upgrades possible.

List of hosts/ip are a combination of 2 lists allowing overrides

Each role has to know how to deal with the other.
Otherwise, depending on order of execution, the firewall might not
allow connections for evomaintenance

Copied from
https://forge.evolix.org/projects/minifirewall/repository/revisions/master/entry/minifirewall.conf