Allow allowed_hosts to not have ipv6 interfaces

This puts a conditional around the AAAA lookup so we can add hosts in
clouds that don't provide an IPv6 address.

Change-Id: I97e82a41fdbe31e7bce6f05b8e6aa39834c42548

templates/rules.v6.erb

@@ -25,10 +25,13 @@
 <% @rules6.each do |rule| -%>
 -A openstack-INPUT <%= rule %>
 <% end -%>
+<% begin -%>
 <% @allowed_hosts.each do |host| -%>
 <% scope.call_function('dns_aaaa', [host['hostname']]).each do |addr| -%>
 -A openstack-INPUT <% if host['protocol'] == 'tcp' %>-m state --state NEW <% end -%>-m <%= host['protocol'] %> -p <%= host['protocol'] %> -s <%= addr %> --dport <%= host['port'] %> -j ACCEPT
 <% end -%>
 <% end -%>
+<% rescue Resolv::ResolvError -%>
+<% end -%>
 -A openstack-INPUT -j REJECT --reject-with icmp6-adm-prohibited
 COMMIT