Merge "Prevent execute app transition too early when performClearTask" into sc-v2-dev am: f49cb0da83 am: 2034ed1177

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15784351

Change-Id: I1f227fb1e76729fb0b8e28e1ec1b8e350323b8b0