Automatic merge from submit-queue

Fix sort-by output problem

Fixes https://github.com/kubernetes/kubectl/issues/43

This bug was original introduced in pr here: https://github.com/kubernetes/kubernetes/pull/46265, I think next time if we touch something printer related package, maybe should let @smarterclayton have a review, although he is pretty busy I guess : ) and that package also changed a lot recently since he's been working on refactoring.
 
this is a quick and dirty fix, not sure if there's better way, I will add some regression test soon...

@kubernetes/sig-cli-pr-reviews 

```release-note
NONE
```

/assign @mengqiy 
/assign @smarterclayton