fix configmap-pod CrashLoopBackOff

Author: hchyue

content/en/docs/concepts/storage/volumes.md

@@ -174,6 +174,7 @@ spec:
   containers:
     - name: test
       image: busybox:1.28
+      command: ['sh', '-c', 'echo The app is running! && sleep 3600']
       volumeMounts:
         - name: config-vol
           mountPath: /etc/config