Merge pull request kubernetes#127435 from sttts/sttts-getmanagedfields-nocopy

unstructured: avoid deepcopying managedFields

Author: k8s-ci-robot

staging/src/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured/unstructured.go

@@ -450,10 +450,14 @@ func (u *Unstructured) SetFinalizers(finalizers []string) {
 }
 
 func (u *Unstructured) GetManagedFields() []metav1.ManagedFieldsEntry {
-	items, found, err := NestedSlice(u.Object, "metadata", "managedFields")
+	v, found, err := NestedFieldNoCopy(u.Object, "metadata", "managedFields")
 	if !found || err != nil {
 		return nil
 	}
+	items, ok := v.([]interface{})
+	if !ok {
+		return nil
+	}
 	managedFields := []metav1.ManagedFieldsEntry{}
 	for _, item := range items {
 		m, ok := item.(map[string]interface{})