Back PlatformKeyManager with database

It was previously using SharedPreferences

Test: adb shell am instrument -w -e package com.android.server.locksettings.recoverablekeystore com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner
Change-Id: I76a75edb93a3feca645e49162c0d8b3e9485385b
2 files changed