kubectl delete doesn't return error or print resource not found

If you run `kubectl delete resource <non_existent_resource_name>`, kubectl exits with 0 and prints nothing.

E.g.

```
$ ./cluster/kubectl.sh delete pod abc
$ echo $?
0
```

I expected to see a "resource not found" message and/or an error code when this occurred. It's very misleading when you type the wrong resource name and think you delete it.
