Automatic merge from submit-queue (batch tested with PRs 51401, 54056, 54977, 55017, 55052). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

[cli] exit when Validate() returns an error

cmdutil.UsageErrorf() does nothing but returna a string. When Validate()
returns an error, we should call exit() function.

fix: https://github.com/kubernetes/kubectl/issues/119

**Release note**:
```
NONE
```