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

This reverts commit e290de5ecdd591d1978af1b0e9b3303696c849ed.

Change-Id: I5c30ef4560bed7c83243517ba8868069f2777613

Conflicts:

	services/java/com/android/server/am/UsageStatsService.java