[MODULES-5924] Fix unmanaged rule regex when updating a iptable.

[MODULES-5924] Fix unmanaged rule regex when updating a iptable.

We have two kind of unmanaged rules:

- empty comment: those get an md5 hash as a name prefixed with 90XX
- comment not matching “\d[graph,space]+$”

This is defined there[1]

But when we calculate the updated line we take into account only the
first kind of unmanaged rule in the offset[2] which leads to error.

Relaxing the regex solves this.

[1] https://github.com/puppetlabs/puppetlabs-firewall/blob/master/lib/puppet/provider/firewall/iptables.rb#L610..L617
[2] https://github.com/puppetlabs/puppetlabs-firewall/blob/master/lib/puppet/provider/firewall/iptables.rb#L802..L803