fix: mount tmp emptyDir to stop CoreDNS restarts (#949)

* revert: skip dns-liveness restarts check for k8s 1.14 (#931)

This reverts commit 9141412.

* fix: add tmp emptyDir to work around CoreDNS 1.3.1 restarting

parts/k8s/addons/coredns.yaml

@@ -149,6 +149,8 @@ spec:
         - name: config-volume
           mountPath: /etc/coredns
           readOnly: true
+        - name: tmp
+          mountPath: /tmp
         ports:
         - containerPort: 53
           name: dns
@@ -178,6 +180,8 @@ spec:
           readOnlyRootFilesystem: true
       dnsPolicy: Default
       volumes:
+        - name: tmp
+          emptyDir: {}
         - name: config-volume
           configMap:
             name: coredns

test/e2e/kubernetes/kubernetes_test.go

@@ -1465,7 +1465,7 @@ var _ = Describe("Azure Container Cluster using the Kubernetes Orchestrator", fu
 
 	Describe("after the cluster has been up for awhile", func() {
 		It("dns-liveness pod should not have any restarts", func() {
-			if !eng.HasNetworkPolicy("calico") && !common.IsKubernetesVersionGe(eng.ExpandedDefinition.Properties.OrchestratorProfile.OrchestratorVersion, "1.14.0") {
+			if !eng.HasNetworkPolicy("calico") {
 				pod, err := pod.Get("dns-liveness", "default")
 				Expect(err).NotTo(HaveOccurred())
 				running, err := pod.WaitOnReady(retryTimeWhenWaitingForPodReady, 3*time.Minute)