Ensure that "media only" button isn't always set

If the "allow all files" button in the AppPermissionFragment has been
checked, ensure we do not mark the "allow for media only" button as
checked by accident.

Fixes: 157476812
Test: Go to the AppPermissionFragment of the files and media permission
of the Files app. It should have "allow management of all files"
checked.

Change-Id: Ia87e9131d14a34ad5a5e8033eb19ba4890d4f7d4