Ignore callbacks from the non-active hardware composer

Ignore callbacks from the non-active hardware composer so we don't get
e.g. duplicate vsync callbacks, one from each composer.

Bug: None

Test: Manually confirmed with logs we're now ignoring callbacks on the
      non-active composer.

Change-Id: I8b475d6283d86c64ff96b41e78528bce8c6ff1d3
diff --git a/libs/vr/libvrflinger/display_service.cpp b/libs/vr/libvrflinger/display_service.cpp
index c464c98..5309acf 100644
--- a/libs/vr/libvrflinger/display_service.cpp
+++ b/libs/vr/libvrflinger/display_service.cpp
@@ -318,6 +318,10 @@
   return hardware_composer_.SetDisplaySurfaces(std::move(visible_surfaces));
 }
 
+void DisplayService::OnHardwareComposerRefresh() {
+  hardware_composer_.OnHardwareComposerRefresh();
+}
+
 void DisplayService::SetDisplayConfigurationUpdateNotifier(
     DisplayConfigurationUpdateNotifier update_notifier) {
   update_notifier_ = update_notifier;