8487: Allow override of default CoreDNS zone cache (#8488)

Using the coredns_cluster_zone_cache_block variable

roles/kubernetes-apps/ansible/defaults/main.yml

@@ -11,6 +11,8 @@ enable_coredns_reverse_dns_lookups: true
 coredns_ordinal_suffix: ""
 # dns_extra_tolerations: [{effect: NoSchedule, operator: "Exists"}]
 coredns_deployment_nodeselector: "kubernetes.io/os: linux"
+coredns_default_zone_cache_block: |
+  cache 30
 
 # nodelocaldns
 nodelocaldns_cpu_requests: 100m

roles/kubernetes-apps/ansible/templates/coredns-config.yml.j2

@@ -53,7 +53,7 @@ data:
 {% if enable_coredns_k8s_external %}
         k8s_external {{ coredns_k8s_external_zone }}
 {% endif %}
-        cache 30
+        {{ coredns_default_zone_cache_block | indent(width=8, first=False) }}
         loop
         reload
         loadbalance