Merge pull request #58760 from mtaufen/kc-remove-kubeletconfigfile-gate

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>.

Removal of KubeletConfigFile feature gate: Step 1

This feature gate was redundant with the `--config` flag, which already
enables/disables loading Kubelet config from a file.

Since the gate guarded an alpha feature, removing it is not a violation
of our API guidelines.

Some stuff in `kubernetes/test-infra` currently sets the gate,
so removing will be a 3 step process:
1. This PR, which makes the gate a no-op.
2. Stop setting the gate in `kubernetes/test-infra`.
3. Completely remove the gate (this PR will get the release note).

```release-note
NONE
```

cmd/kubelet/app/server.go

@@ -930,14 +930,13 @@ func parseResourceList(m map[string]string) (v1.ResourceList, error) {
 
 // BootstrapKubeletConfigController constructs and bootstrap a configuration controller
 func BootstrapKubeletConfigController(defaultConfig *kubeletconfiginternal.KubeletConfiguration,
-	kubeletConfigFileFlag flag.StringFlag,
+	kubeletConfigFile string,
 	dynamicConfigDirFlag flag.StringFlag) (*kubeletconfiginternal.KubeletConfiguration, *kubeletconfig.Controller, error) {
 	var err error
 	// Alpha Dynamic Configuration Implementation; this section only loads config from disk, it does not contact the API server
 	// compute absolute paths based on current working dir
-	kubeletConfigFile := ""
-	if utilfeature.DefaultFeatureGate.Enabled(features.KubeletConfigFile) && kubeletConfigFileFlag.Provided() {
-		kubeletConfigFile, err = filepath.Abs(kubeletConfigFileFlag.Value())
+	if len(kubeletConfigFile) > 0 {
+		kubeletConfigFile, err = filepath.Abs(kubeletConfigFile)
 		if err != nil {
 			return nil, nil, fmt.Errorf("failed to get absolute path for --config")
 		}