FIX: Firewall state custom host group assignments for single portgroup entry

[m0duspwnens]

If a single portgroup is added to a custom hostgroup assignment for a role, it is treated as a string and not a list of string. We need to force the type to be a list of strings.

          ID: iptables_config
    Function: file.managed
        Name: /etc/sysconfig/iptables
      Result: False
     Comment: Unable to manage file: Jinja variable 'dict object' has no attribute 'c'; line 79

              ---
              [...]

              {%- for chn, hostgroups in FIREWALL_MERGED.role[role].chain.items() %}
              {%-   for hostgroup, portgroups in hostgroups['hostgroups'].items() %}
              {%-     for ip in FIREWALL_MERGED.hostgroups[hostgroup] %}
              {%-       for groupname in portgroups['portgroups'] %}
              {%-         for proto, ports in FIREWALL_MERGED['portgroups'][groupname].items() %}    <======================
              {%-           for port in ports %}
              -A {{chn}} -s {{ip}} -p {{proto}} -m {{proto}} --dport {{port}} -j ACCEPT
              {%-           endfor %}
              {%-         endfor %}
              {%-       endfor %}
              [...]
              ---
     Started: 14:51:29.452646
    Duration: 320.204 ms
     Changes: