kubeadm: add the preferred pod anti-affinity for CoreDNS Deployment

cmd/kubeadm/app/phases/addons/dns/manifests.go

@@ -78,6 +78,17 @@ spec:
     spec:
       priorityClassName: system-cluster-critical
       serviceAccountName: coredns
+      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