Add support for running a nodelocal dns cache (#3861)

* Add support for running a nodelocal dns cache

After encountering dns issues in a cluster I was recently working on I
noticed Kubernetes 1.13 introduced support for running a nodelocal dns
cache.

I believe this can usefull for more people.

73b548db06
https://github.com/kubernetes/enhancements/blob/master/keps/sig-network/0030-nodelocal-dns-cache.md

* Add requested changes

* Add additional requested changes + documentation

* Add requested changes after review

* Replace incorrect variable

roles/download/defaults/main.yml

@@ -184,6 +184,10 @@ coredns_version: "1.2.6"
 coredns_image_repo: "coredns/coredns"
 coredns_image_tag: "{{ coredns_version }}"
 
+nodelocaldns_version: "1.15.0"
+nodelocaldns_image_repo: "k8s.gcr.io/k8s-dns-node-cache"
+nodelocaldns_image_tag: "{{ nodelocaldns_version }}"
+
 dnsmasq_nanny_image_repo: "gcr.io/google_containers/k8s-dns-dnsmasq-nanny-{{ image_arch }}"
 dnsmasq_nanny_image_tag: "{{ kubedns_version }}"
 dnsmasq_sidecar_image_repo: "gcr.io/google_containers/k8s-dns-sidecar-{{ image_arch }}"
@@ -490,6 +494,15 @@ downloads:
     groups:
       - kube-node
 
+  nodelocaldns:
+    enabled: "{{ enable_nodelocaldns == True }}"
+    container: true
+    repo: "{{ nodelocaldns_image_repo }}"
+    tag: "{{ nodelocaldns_image_tag }}"
+    sha256: "{{ nodelocaldns_digest_checksum|default(None) }}"
+    groups:
+      - kube-node
+
   dnsmasq_nanny:
     enabled: "{{ dns_mode in ['kubedns', 'dnsmasq_kubedns'] }}"
     container: true