vncflinger: fix API usage  of setDisplayLayerStack

it now ui::DEFAULT_LAYER_STACK

Change-Id: Id692b073922808c9cfe0dd04f23d94375af73409
diff --git a/src/VirtualDisplay.cpp b/src/VirtualDisplay.cpp
index 3122ca8..3822f14 100644
--- a/src/VirtualDisplay.cpp
+++ b/src/VirtualDisplay.cpp
@@ -56,7 +56,7 @@
     SurfaceComposerClient::Transaction t;
     t.setDisplaySurface(mDisplayToken, mProducer);
     t.setDisplayProjection(mDisplayToken, state->orientation, mSourceRect, displayRect);
-    t.setDisplayLayerStack(mDisplayToken, 0);  // default stack
+    t.setDisplayLayerStack(mDisplayToken, ui::DEFAULT_LAYER_STACK);  // default stack
     t.apply();
 
     ALOGV("Virtual display (%ux%u [viewport=%ux%u] created", width, height, displayRect.getWidth(),