Merge "Expose systemReady for SystemServer" am: 7af6a2e9f4 am: 151f526613 am: a71f7d4697

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1640142

Change-Id: I95488b39a32ed9086839eab6c457ed6f75472df1