Don't close widget preview cache db

Only one connection is ever held now, and that
will be closed when the app is killed

src/com/android/launcher2/AppsCustomizePagedView.java

@@ -894,9 +894,6 @@ public class AppsCustomizePagedView extends PagedViewWithDraggableItems implemen
     protected void onDetachedFromWindow() {
         super.onDetachedFromWindow();
         cancelAllTasks();
-        if (mWidgetPreviewLoader != null) {
-            mWidgetPreviewLoader.closeDb();
-        }
     }
 
     public void clearAllWidgetPages() {

src/com/android/launcher2/WidgetPreviewLoader.java

@@ -348,7 +348,6 @@ public class WidgetPreviewLoader {
                             WIDGET_PREFIX + packageName + "/%",
                             SHORTCUT_PREFIX + packageName + "/%"} // args to SELECT query
                             );
-                db.close();
                 synchronized(sInvalidPackages) {
                     sInvalidPackages.remove(packageName);
                 }
@@ -357,12 +356,6 @@ public class WidgetPreviewLoader {
         }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, (Void) null);
     }
 
-    public void closeDb()  {
-        if (mDb != null) {
-            mDb.close();
-        }
-    }
-
     private Bitmap readFromDb(String name, Bitmap b) {
         if (mCachedSelectQuery == null) {
             mCachedSelectQuery = CacheDb.COLUMN_NAME + " = ? AND " +