nameserver: Allow master server to notify via ipv6

Logs show that the nameservers are being notified via ipv6 and
rejecting the request:

  nsd[18851]: notify for acme.opendev.org. \
   from 2001:4800:7819:104:be76:4eff:fe04:43d0 refused, no acl matches.

Modify the nsd ACL to allow the ipv6 of the master to trigger updates.
This is important for the letsencrypt process, where we need the
acme.opendev.org domain updated in a timely fashion so that TXT
authentication works.

Change-Id: I785f9636dd05e15b8ffd211845f439be7e8344a3

inventory/service/group_vars/dns.yaml

@@ -16,4 +16,5 @@ dns_zones:
 dns_notify:
   - 104.239.140.165
   - 162.253.55.16
-dns_master: 104.239.146.24
+dns_master_ipv4: 104.239.146.24
+dns_master_ipv6: 2001:4800:7819:104:be76:4eff:fe04:43d0

playbooks/roles/nameserver/README.rst

@@ -37,6 +37,10 @@ nameserver.
       located at ``zones/example_com/zone.db``, then the value here
       should be ``example.com/zones/example_com``.
 
-.. zuul:rolevar:: dns_master
+.. zuul:rolevar:: dns_master_ipv4
 
-   The IP addresses of the master nameserver.
+   Required argument.  The IPv4 addresses of the master nameserver.
+
+.. zuul:rolevar:: dns_master_ipv6
+
+   Required argument.  The IPv6 addresses of the master nameserver.

playbooks/roles/nameserver/templates/nsd.conf.j2

@@ -35,6 +35,7 @@ key:
 {% for zone in dns_zones %}
 zone:
     name: {{ zone.name }}
-    allow-notify: {{ dns_master }} NOKEY
-    request-xfr: AXFR {{ dns_master }} tsig
+    allow-notify: {{ dns_master_ipv4 }} NOKEY
+    allow-notify: {{ dns_master_ipv6 }} NOKEY
+    request-xfr: AXFR {{ dns_master_ipv4 }} tsig
 {% endfor %}