Fetch the wallpaper category from the server instead of cache when launching...

Fetch the wallpaper category from the server instead of cache when launching the app(activity). am: ab03e09b

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/ThemePicker/+/12660783

Change-Id: I473c26ec37e3c4307c090c85bc70c87f7e751b57