Locking changes in ProcessedPackagesJournal

A follow-up CL to apply the code feedback from the first one.

Bug: 36850431
Test: adb shell am instrument -w -e package com.android.server.backup com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner
Change-Id: I8785eb358658757b329ac871194243c47e6d87a9
4 files changed