enable correct service for EL9 using legacy IPv4

probably not many people still using IPv4 in their systems, after all
IPv6 is soon 25 years old, but... we still want to support it.

nftables.service loads nft rules from /etc/sysconfig/nftables.conf,
but this module generates classic iptables rules.  The service to load
these on boot is simply "iptables.service".

IPv6 rules are loaded correctly by ip6tables.service.

manifests/params.pp

@@ -30,7 +30,7 @@
         }
         default: {
           if versioncmp($::operatingsystemrelease, '9') >= 0 {
-            $service_name = 'nftables'
+            $service_name = 'iptables'
             $service_name_v6 = 'ip6tables'
             $package_name = ['iptables-services', 'nftables', 'iptables-nft-services']
             $iptables_name = 'iptables-nft'