dch-gw: Add IPv6 ULA prefix to pyrocufflink.blue

For internal services, particularly DNS, it is easier to use a ULA
prefix than rely exclusively on routed addresses, since these can change
relatively frequently.

group_vars/dch-gw/radvd.yml

@@ -8,6 +8,8 @@ radvd_interfaces:
 - interface: '{{ dch_networks.blue.router_iface }}'
   prefixes:
   - prefix: '::/64'
+  rdnss: '{{ dch_networks.blue.dns_servers }}'
+  dnssl: '{{ dch_networks.blue.dns_search }}'
 
 - interface: '{{ dch_networks.red.router_iface }}'
   prefixes: