Add back anti-affinity to kube-dns pods.

This change also updates to the latest kube-dns images. The
anti-affinity change was previously rolled back in https://github.com/kubernetes/kubernetes/pull/59357
Adding this back as there have been imrpovements in scheduler
performance since.

cluster/addons/dns/kube-dns/kube-dns.yaml.base

@@ -90,6 +90,17 @@ spec:
       securityContext:
         supplementalGroups: [ 65534 ]
         fsGroup: 65534
+      affinity:
+        podAntiAffinity:
+          preferredDuringSchedulingIgnoredDuringExecution:
+          - weight: 100
+            podAffinityTerm:
+              labelSelector:
+                matchExpressions:
+                  - key: k8s-app
+                    operator: In
+                    values: ["kube-dns"]
+              topologyKey: kubernetes.io/hostname
       tolerations:
       - key: "CriticalAddonsOnly"
         operator: "Exists"

cluster/addons/dns/kube-dns/kube-dns.yaml.in

@@ -90,6 +90,17 @@ spec:
       securityContext:
         supplementalGroups: [ 65534 ]
         fsGroup: 65534
+      affinity:
+        podAntiAffinity:
+          preferredDuringSchedulingIgnoredDuringExecution:
+          - weight: 100
+            podAffinityTerm:
+              labelSelector:
+                matchExpressions:
+                  - key: k8s-app
+                    operator: In
+                    values: ["kube-dns"]
+              topologyKey: kubernetes.io/hostname
       tolerations:
       - key: "CriticalAddonsOnly"
         operator: "Exists"

cluster/addons/dns/kube-dns/kube-dns.yaml.sed

@@ -90,6 +90,17 @@ spec:
       securityContext:
         supplementalGroups: [ 65534 ]
         fsGroup: 65534
+      affinity:
+        podAntiAffinity:
+          preferredDuringSchedulingIgnoredDuringExecution:
+          - weight: 100
+            podAffinityTerm:
+              labelSelector:
+                matchExpressions:
+                  - key: k8s-app
+                    operator: In
+                    values: ["kube-dns"]
+              topologyKey: kubernetes.io/hostname
       tolerations:
       - key: "CriticalAddonsOnly"
         operator: "Exists"