Don't show the outline on the current page

- only on sw720dp+ devices

Change-Id: I7253bedbf6dd61c766fe7e9ad861d3a917d37fed
diff --git a/src/com/android/launcher2/CellLayout.java b/src/com/android/launcher2/CellLayout.java
index ba20a76..89c623e 100644
--- a/src/com/android/launcher2/CellLayout.java
+++ b/src/com/android/launcher2/CellLayout.java
@@ -1045,7 +1045,10 @@
     }
 
     public void setBackgroundAlphaMultiplier(float multiplier) {
-        mBackgroundAlphaMultiplier = multiplier;
+        if (mBackgroundAlphaMultiplier != multiplier) {
+            mBackgroundAlphaMultiplier = multiplier;
+            invalidate();
+        }
     }
 
     public float getBackgroundAlphaMultiplier() {