Be more lenient about live wallpaper unavailability

- Give the app 5 more seconds to restart following a crash
- Presume that system-default wallpapers are robust, and don't fall back
  to showing nothing at all if timing or update problems arise
- Improve logging about static imagery handling during boot
- For now, turn on a bit more logging about wallpaper activity

Bug 36573894
Bug 34979999
Test: manual

Change-Id: I787a351f1251b83451d55bb98a4e0de9ce17836a