Use dnsutils image for DNS debugging (#18001)

DNS debugging documentation is using a busybox image as example.
This image has different known issues with the way it resolves
the DNS names in k8s, creating confusion with users that try to
follow the docs.

The e2e tests use a custom small image ~4.3MB for DNS testing
with all the necessary tools. Also, the fact that this image is
being used for the k8s e2e testing guarantees it's compatibility.

content/en/docs/tasks/administer-cluster/dns-debugging-resolution.md

@@ -20,26 +20,26 @@ This page provides hints on diagnosing DNS problems.
 
 ### Create a simple Pod to use as a test environment
 
-Create a file named busybox.yaml with the following contents:
+Create a file named dnsutils.yaml with the following contents:
 
-{{< codenew file="admin/dns/busybox.yaml" >}}
+{{< codenew file="admin/dns/dnsutils.yaml" >}}
 
 Then create a pod using this file and verify its status:
 
 ```shell
-kubectl apply -f https://k8s.io/examples/admin/dns/busybox.yaml
-pod/busybox created
+kubectl apply -f https://k8s.io/examples/admin/dns/dnsutils.yaml
+pod/dnsutils created
 
-kubectl get pods busybox
+kubectl get pods dnsutils
 NAME      READY     STATUS    RESTARTS   AGE
-busybox   1/1       Running   0          <some-time>
+dnsutils   1/1       Running   0          <some-time>
 ```
 
 Once that pod is running, you can exec `nslookup` in that environment.
 If you see something like the following, DNS is working correctly.
 
 ```shell
-kubectl exec -ti busybox -- nslookup kubernetes.default
+kubectl exec -ti dnsutils -- nslookup kubernetes.default
 Server:    10.0.0.10
 Address 1: 10.0.0.10
 
@@ -56,7 +56,7 @@ Take a look inside the resolv.conf file.
 [Known issues](#known-issues) below for more information)
 
 ```shell
-kubectl exec busybox cat /etc/resolv.conf
+kubectl exec dnsutils cat /etc/resolv.conf
 ```
 
 Verify that the search path and name server are set up like the following
@@ -72,7 +72,7 @@ Errors such as the following indicate a problem with the coredns/kube-dns add-on
 associated Services:
 
 ```
-kubectl exec -ti busybox -- nslookup kubernetes.default
+kubectl exec -ti dnsutils -- nslookup kubernetes.default
 Server:    10.0.0.10
 Address 1: 10.0.0.10
 
@@ -82,7 +82,7 @@ nslookup: can't resolve 'kubernetes.default'
 or
 
 ```
-kubectl exec -ti busybox -- nslookup kubernetes.default
+kubectl exec -ti dnsutils -- nslookup kubernetes.default
 Server:    10.0.0.10
 Address 1: 10.0.0.10 kube-dns.kube-system.svc.cluster.local
 

content/en/examples/admin/dns/dnsutils.yaml

@@ -0,0 +1,14 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: dnsutils
+  namespace: default
+spec:
+  containers:
+  - name: dnsutils
+    image: gcr.io/kubernetes-e2e-test-images/dnsutils:1.3
+    command:
+      - sleep
+      - "3600"
+    imagePullPolicy: IfNotPresent
+  restartPolicy: Always