Merge pull request #36980 from tanshanshan/ifelse-modify

Automatic merge from submit-queue

 replace if with else-if

<!--  Thanks for sending a pull request!  Here are some tips for you:
1. If this is your first time, read our contributor guidelines https://github.com/kubernetes/kubernetes/blob/master/CONTRIBUTING.md and developer guide https://github.com/kubernetes/kubernetes/blob/master/docs/devel/development.md
2. If you want *faster* PR reviews, read how: https://github.com/kubernetes/kubernetes/blob/master/docs/devel/faster_reviews.md
3. Follow the instructions for writing a release note: https://github.com/kubernetes/kubernetes/blob/master/docs/devel/pull-requests.md#release-notes
-->

**What this PR does / why we need it**:

I replace if with else-if

Thanks!

**Special notes for your reviewer**:

**Release note**:
<!--  Steps to write your release note:
1. Use the release-note-* labels to set the release note state (if you have access) 
2. Enter your extended release note in the below block; leaving it blank means using the PR title as the release note. If no release note is required, just write `NONE`. 
-->
```release-note
```

pkg/util/validation/validation.go

@@ -283,8 +283,7 @@ func IsConfigMapKey(value string) []string {
 	}
 	if value == "." {
 		errs = append(errs, `must not be '.'`)
-	}
-	if value == ".." {
+	} else if value == ".." {
 		errs = append(errs, `must not be '..'`)
 	} else if strings.HasPrefix(value, "..") {
 		errs = append(errs, `must not start with '..'`)