Always define a multicast network for jgroups

templates/iptables-rules.v4.j2

@@ -224,9 +224,7 @@
 -A INPUT -m state --state NEW -p tcp -m tcp --dport {{ jgroups_multicast_port }} -j ACCEPT
 -A INPUT -p udp -m udp --dport {{ jgroups_multicast_port }} -j ACCEPT
 {% endif %}
-{% if jgroups_multicast_net is defined %}
--A INPUT -d {{ jgroups_multicast_net }} -j ACCEPT
-{% endif %}
+-A INPUT --protocol igmp -d {{ jgroups_multicast_net | default('224.0.0.0/4') }} -j ACCEPT
 {% endif %}
 
 {% if docker_swarm is defined and docker_swarm %}