batstats: fix wake lock tracking, service bug

- Fix bug I introduced in handling wake lock changes where
  we weren't iterating over the new work sources correctly.
- Fix bug in ActiveServices that would wtf too much.
- Prepare to start tracking uptime in the battery history.

Change-Id: Ia94316be51bc6eab7b02f214a5c40c08e99cc3b1
4 files changed