Support burst in stateful set scale up and down

The alpha field podManagementPolicy defines how pods are created,
deleted, and replaced. The new `Parallel` policy will replace pods
as fast as possible, not waiting for the pod to be `Ready` or providing
an order. This allows for advanced clustered software to take advantage
of rapid changes in scale.

pkg/controller/statefulset/stateful_set_utils.go

@@ -227,6 +227,11 @@ func isHealthy(pod *v1.Pod) bool {
 	return isRunningAndReady(pod) && !isTerminating(pod)
 }
 
+// allowsBurst is true if the alpha burst annotation is set.
+func allowsBurst(set *apps.StatefulSet) bool {
+	return set.Annotations[apps.StatefulSetBurstAnnotation] == "true"
+}
+
 // newControllerRef returns an ControllerRef pointing to a given StatefulSet.
 func newControllerRef(set *apps.StatefulSet) *metav1.OwnerReference {
 	blockOwnerDeletion := true