Always set transition ready in executeAppTransition.

To set the transition ready signal even if the top resumed activity is
in a TaskFragment.

Flag: EXEMPT bugfix
Bug: 380830218
Test: atest ActivityLifecycleTests ActivityLifecycleTopResumedStateTests
Test: Launch an app that has use activity embedded for its activity,
move the app to desktop windowing mode, then launch another app. Close
the last app with finish and verify there won't encounter transition
timeout.

Change-Id: Ifed7edad77b9b7c67147a903ba538fd85ec10af0