docker: ensure br_netfilter is loaded until fixed upstream

Author: saltydk

roles/docker/tasks/subtasks/daemon.yml

@@ -24,6 +24,7 @@
       fixed-cidr-v6: "{{ '2001:db8::/64'
                       if docker_ipv6
                       else omit }}"
+      iptables: true
       ip6tables: "{{ true
                   if docker_ipv6
                   else false }}"

roles/docker/templates/override.conf.j2

@@ -19,4 +19,5 @@ Requires={{ docker_service_after }}
 Wants=saltbox_managed_docker_controller_helper.service saltbox_managed_docker_update_hosts.service
 
 [Service]
+ExecStartPre=modprobe -va bridge br_netfilter
 ExecStartPre=/bin/sleep {{ docker_service_sleep }}