Fix a bootloop problem when /data/system/usagestats/usage-history.xml is empty.
This often occurs after an incomplete reboot/shutdown or battery pull.

Patchset 2: Cleanup
Patchset 3: More Cleanup
Patchset 4: derp

Change-Id: I4f01151f4051df4ae1b85fa460ec7a9e70122878
Merge "Fix a bootloop problem when /data/system/usagestats/usage-history.xml is empty. This often occurs after an incomplete reboot/shutdown or battery pull." into android-4.4