Disable Virtual Display by default in SF

These should be enabled by default once b/30022738 is resolved.

Change-Id: I70a48a0bcf98ca984a28aa130170270d16e708bf
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 55735b1..cd6914b 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -532,7 +532,7 @@
     bool mPropagateBackpressure = true;
 #endif
     SurfaceInterceptor mInterceptor;
-    bool mUseHwcVirtualDisplays = true;
+    bool mUseHwcVirtualDisplays = false;
 
     // Restrict layers to use two buffers in their bufferqueues.
     bool mLayerTripleBufferingDisabled = false;