controller: don't count replica count in revision hash calculation (#10)

Previous fix to prevent replica count update causing full
regionserver restart has few drawbacks due to the fact that
hash calculation is still based on historical statefulset count,
which means any time CRD's current replica count is incorrect
(i.e. CRD is out of sync, operator crashed and never finished
reconciliation run successfully, act of nature...) this still
creates a new hash that causes regionservers to erroroneously
restart.

We're removing replica count altogether from revision hash
calculation, and accepting the operational risk that the first time
this logic is introduced it will restart all components as revision
hash will be different.

controllers/hbase_controller.go

@@ -572,9 +572,9 @@ func (r *HBaseReconciler) ensureStatefulSetPods(ctx context.Context, sts *appsv1
 func (r *HBaseReconciler) ensureStatefulSet(hb *hbasev1.HBase,
 	stsName, cmName types.NamespacedName, ss hbasev1.ServerSpec) (*appsv1.StatefulSet, bool, error) {
 	actual := &appsv1.StatefulSet{}
+	expected, expectedRevision := r.statefulSet(hb, stsName, cmName, ss)
 	if err := r.Get(context.TODO(), stsName, actual); err != nil {
 		if errors.IsNotFound(err) {
-			expected, _ := r.statefulSet(hb, stsName, cmName, ss, 0)
 
 			if err = controllerutil.SetControllerReference(hb, expected, r.Scheme); err != nil {
 				return nil, false, err
@@ -587,8 +587,6 @@ func (r *HBaseReconciler) ensureStatefulSet(hb *hbasev1.HBase,
 		}
 		return nil, false, err
 	}
-	expected, expectedRevision := r.statefulSet(hb, stsName, cmName, ss, *actual.Spec.Replicas)
-
 	r.Log.Info("updating revision", "sameRevision", expectedRevision != actual.Annotations[HBaseControllerRevisionKey])
 	r.Log.Info("updating replica count", "sameReplicaCount", *actual.Spec.Replicas != *expected.Spec.Replicas)
 
@@ -643,14 +641,10 @@ const (
 )
 
 func (r *HBaseReconciler) statefulSet(hb *hbasev1.HBase,
-	stsName, cmName types.NamespacedName, ss hbasev1.ServerSpec, rc int32) (*appsv1.StatefulSet, string) {
+	stsName, cmName types.NamespacedName, ss hbasev1.ServerSpec) (*appsv1.StatefulSet, string) {
 	spec := (&ss.PodSpec).DeepCopy()
 	spec.Volumes = append(spec.Volumes, configMapVolume(cmName))
 	stsSpec := appsv1.StatefulSetSpec{
-		// We don't want to use replica value as part of revision change (since
-		// scaling a statefulset is not the same as a new revision) so we just
-		// set current count for now just for hash calculation.
-		Replicas:            pointer.Int32Ptr(rc),
 		PodManagementPolicy: appsv1.ParallelPodManagement,
 		// OnDelete because we managed the pod restarts ourselves
 		UpdateStrategy: appsv1.StatefulSetUpdateStrategy{