Finish recents animation when launching another task in Overview

App open animation gets cancelled because of screenshot cleanup (launcher is stopped). We need window manager support to allow them to go parallel (b/143774568). As a workaround, we can either (1) delay launching the next task until recents animation is properly cancelled (2) finish the recents animation before launching the next task. Performance is the same, so go with (2) since it's a cleaner solution

Fixes: 143773683
Test: Swipe up to Overview from app, launch another task in Overview. See everything animate smoothly.
Change-Id: Iafd3f6f529fba32c1113b766c033e5932f19f4f3