Fix issue #6761130: Clearing app data in settings does not clear app's USB storage

The installed app details was not correctly distinguishing between cache and
normal data on external storage.  The cache files on external storage are now
correctly shown in the cache section, since those are what get deleted when
you hit the clear cache button.

Change-Id: Id98bdb7fb5202d6a092fe5a772638eeb6aed2b47