Merge pull request #39718 from foxish/remove-statefulset-special-case

Automatic merge from submit-queue (batch tested with PRs 39230, 39718)

Remove special case for StatefulSets in scheduler

**What this PR does / why we need it**: Removes special case for StatefulSet in scheduler code
/ref: https://github.com/kubernetes/kubernetes/issues/39687

**Special notes for your reviewer**:

**Release note**:

```release-note
Scheduler treats StatefulSet pods as belonging to a single equivalence class.
```

plugin/pkg/scheduler/algorithmprovider/defaults/defaults.go

@@ -238,7 +238,7 @@ func GetEquivalencePod(pod *v1.Pod) interface{} {
 	// to be equivalent
 	if len(pod.OwnerReferences) != 0 {
 		for _, ref := range pod.OwnerReferences {
-			if *ref.Controller && isValidControllerKind(ref.Kind) {
+			if *ref.Controller {
 				equivalencePod.ControllerRef = ref
 				// a pod can only belongs to one controller
 				break
@@ -248,17 +248,6 @@ func GetEquivalencePod(pod *v1.Pod) interface{} {
 	return &equivalencePod
 }
 
-// isValidControllerKind checks if a given controller's kind can be applied to equivalence pod algorithm.
-func isValidControllerKind(kind string) bool {
-	switch kind {
-	// list of kinds that we cannot handle
-	case StatefulSetKind:
-		return false
-	default:
-		return true
-	}
-}
-
 // EquivalencePod is a group of pod attributes which can be reused as equivalence to schedule other pods.
 type EquivalencePod struct {
 	ControllerRef metav1.OwnerReference