Check if a visible layer exists instead of an invisible layer exists

Multiple layers may exist at index 0 and what we really want to know
is if any of them are active, not if any aren't.

Bug: 36867186, 36036583
Test: Launch ithaca then youtube
Change-Id: I5881a838c7df8670fa42eece558717140d4cb021
diff --git a/libs/vr/libvrflinger/display_service.cpp b/libs/vr/libvrflinger/display_service.cpp
index 3750ea3..bb8613c 100644
--- a/libs/vr/libvrflinger/display_service.cpp
+++ b/libs/vr/libvrflinger/display_service.cpp
@@ -361,10 +361,10 @@
 }
 
 int DisplayService::IsVrAppRunning(pdx::Message& message) {
-  bool visible = true;
+  bool visible = false;
   ForEachDisplaySurface([&visible](const std::shared_ptr<DisplaySurface>& surface) {
-    if (surface->client_z_order() == 0 && !surface->IsVisible())
-      visible = false;
+    if (surface->client_z_order() == 0 && surface->IsVisible())
+      visible = true;
   });
 
   REPLY_SUCCESS_RETURN(message, visible, 0);