[wayland] Make sure that only the fading popups effect animates outline

Summary:
Window open/close animation effects should not animate the outline
because the end result is a bit awkward.

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D19886