Fix issue with some home button presses being ignored.

We are ignoring home button presses after panning away from
the default screen, when the workspace is still moving slightly.

Also, make the home button a no-op when the user is in the
middle of panning the screen (i.e. finger is still down).

Change-Id: Ida6bad4faaf90b6802aac2cbf3444f76b7b38100

src/com/android/launcher2/Workspace.java

@@ -419,8 +419,8 @@ public class Workspace extends SmoothPagedView
         return folders;
     }
 
-    boolean isDefaultPageShowing() {
-        return mCurrentPage == mDefaultPage;
+    boolean isTouchActive() {
+        return mTouchState != TOUCH_STATE_REST;
     }
 
     /**