fix busybox image to 1.28 (issues with nslookup).

Changes where done with these commands:

reprec 'image: busybox(?!:)' 'image: busybox:1.28' */docs */examples
reprec -- '--image=busybox(?!:)' '--image=busybox:1.28' */docs */examples

Related issues:

 https://github.com/docker-library/busybox/issues/48
 https://github.com/kubernetes/kubernetes/issues/66924

content/en/docs/tasks/debug-application-cluster/debug-running-pod.md

@@ -110,7 +110,7 @@ specify the `-i`/`--interactive` argument, `kubectl` will automatically attach
 to the console of the Ephemeral Container.
 
 ```shell
-kubectl debug -it ephemeral-demo --image=busybox --target=ephemeral-demo
+kubectl debug -it ephemeral-demo --image=busybox:1.28 --target=ephemeral-demo
 ```
 
 ```
@@ -182,7 +182,7 @@ but you need debugging utilities not included in `busybox`. You can simulate
 this scenario using `kubectl run`:
 
 ```shell
-kubectl run myapp --image=busybox --restart=Never -- sleep 1d
+kubectl run myapp --image=busybox:1.28 --restart=Never -- sleep 1d
 ```
 
 Run this command to create a copy of `myapp` named `myapp-debug` that adds a
@@ -225,7 +225,7 @@ To simulate a crashing application, use `kubectl run` to create a container
 that immediately exits:
 
 ```
-kubectl run --image=busybox myapp -- false
+kubectl run --image=busybox:1.28 myapp -- false
 ```
 
 You can see using `kubectl describe pod myapp` that this container is crashing:
@@ -283,7 +283,7 @@ additional utilities.
 As an example, create a Pod using `kubectl run`:
 
 ```
-kubectl run myapp --image=busybox --restart=Never -- sleep 1d
+kubectl run myapp --image=busybox:1.28 --restart=Never -- sleep 1d
 ```
 
 Now use `kubectl debug` to make a copy and change its container image