Hook up using initialized public key in KeySyncTask

Not sure if this is correct, PTAL. We won't have a specific uid when
the phone is unlocked, only the userId. Should the public key be
uid-specific or just userId-specific?

Test: adb shell am instrument -w -e package com.android.server.locksettings.recoverablekeystore com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner
Change-Id: Ic2ec442c8a283e747542fafa9d7b0462aa185532