add comments to disableNodeLabelSync

Author: Yuvaraj Kakaraparthi

internal/controllers/machine/machine_controller.go

@@ -91,7 +91,11 @@ type Reconciler struct {
 	// nodeDeletionRetryTimeout determines how long the controller will retry deleting a node
 	// during a single reconciliation.
 	nodeDeletionRetryTimeout time.Duration
-	disableNodeLabelSync     bool
+
+	// disableNodeLabelSync should only be used for tests. This is used to skip the parts of
+	// the controller that need SSA as the current test setup does not support SSA.
+	// This flag should be dropped after the tests are migrated to envtest.
+	disableNodeLabelSync bool
 }
 
 func (r *Reconciler) SetupWithManager(ctx context.Context, mgr ctrl.Manager, options controller.Options) error {