Revert "docker: Enable IPv6 (with NAT)"

This reverts commit 3b25d7e0a9.

It somehow removes the default route.

roles/docker/files/daemon.json

@@ -1,7 +1,5 @@
 {
   "log-driver": "journald",
-  "ipv6": true,
-  "fixed-cidr-v6": "fd00:d0ce:d0ce:d0ce::/64",
   "dns": [
     "46.182.19.48",
     "74.82.42.42"

roles/docker/tasks/config.yml

@@ -1,7 +1,4 @@
 ---
-- name: Add IPv6 NAT iptables rules
-  shell: ip6tables -t nat -A POSTROUTING -s fd00:d0ce:d0ce:d0ce::/64 -j MASQUERADE && ip6tables-save > /etc/iptables/rules.v6
-
 - name: add docker configuration
   copy:
     dest: /etc/docker/daemon.json

roles/docker/tasks/packages.yml

@@ -19,8 +19,3 @@
     name: docker-ce
     update_cache: yes
     state: present
-
-- name: install iptables-persistent
-  apt:
-    name: iptables-persistent
-    state: present