Don't encourage people to mount downwardAPI volumes on /etc (#7484)

Because API data volumes like downwardAPI are expected to be fully
managed by Kubernetes and are now mounted read-only, this causes
problems with other files in /etc like /etc/resolv.conf that Docker
tries to add to the volume. Our examples should show such volumes
being mounted to a dedicated subdirectory for the volume.

docs/tasks/inject-data-application/dapi-volume.yaml

@@ -16,15 +16,15 @@ spec:
       command: ["sh", "-c"]
       args:
       - while true; do
-          if [[ -e /etc/labels ]]; then 
-            echo -en '\n\n'; cat /etc/labels; fi;
-          if [[ -e /etc/annotations ]]; then
-            echo -en '\n\n'; cat /etc/annotations; fi;
+          if [[ -e /etc/podinfo/labels ]]; then
+            echo -en '\n\n'; cat /etc/podinfo/labels; fi;
+          if [[ -e /etc/podinfo/annotations ]]; then
+            echo -en '\n\n'; cat /etc/podinfo/annotations; fi;
           sleep 5;
         done;
       volumeMounts:
         - name: podinfo
-          mountPath: /etc
+          mountPath: /etc/podinfo
           readOnly: false
   volumes:
     - name: podinfo