(#9439) fix parsing and deleting existing rules

(#9439) fix parsing and deleting existing rules

Previously we hadn't been able to parse existing rules that were missing
a comment field. This patch fixes that by using an MD5 hash of the iptables
raw line as the name of the property.

We have also cleaned up the way we delete arguments by adding a new
delete_args function to return valid delete_args. Instead of having to work
out the rule order we now just delete the rule based on the specification.