Automatic merge from submit-queue. 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>.
refactor NsenterWriter to utilize pkg/util/nsenter
**What this PR does / why we need it**:
Per [discussion](https://github.com/kubernetes/kubernetes/pull/51771#discussion_r138824451)
Depend on #51771
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
**Special notes for your reviewer**:
**Release note**:
```release-note
None
```
b2091090fc