(MODULES-6029) Skip unparsable rules with warning

(MODULES-6029) Skip unparsable rules with warning

The iptables rules parser has very strict/simplistic expectations
about how iptables rules should look like, and can easily fail to
parse rules that weren't produced by the module itself.

We should ignore the unfitting rules when parsing and produce a
warning rather than causing a fatal error and stopping the Puppet run.