Fetch the wallpaper category from the server instead of cache when launching the app(activity).

Bug: 169029398
Change-Id: Icbbb11c33ae4d4dd7d376a7792d0f685ad809421
diff --git a/src/com/android/wallpaper/model/CategoryProvider.java b/src/com/android/wallpaper/model/CategoryProvider.java
index ceef6b4..b86e6df 100755
--- a/src/com/android/wallpaper/model/CategoryProvider.java
+++ b/src/com/android/wallpaper/model/CategoryProvider.java
@@ -59,4 +59,9 @@
      * Checks if the categories are fetched.
      */
     boolean isCategoriesFetched();
+
+    /**
+     * Resets the fetched categories if needed.
+     */
+    void resetIfNeeded();
 }