Android: Fix duplicate appearance of All Stories heading

The saga of the scary sqlite queries continues!  This should finally get the All Stories heading to always appear exactly once for any of the following test cases:

1. Users with no root-level feeds
2. Users with root-level feeds that have no unread stories
3. Users with root-level feeds that do have unread stories

Tested on a real Nexus One, a real Nexus 4, a simulated Nexus 4, and a simulated Nexus 7.