workspaceAnimation: Do not create clones for override redirect windows
Override redirect windows manage their own positioning and size alone and are always sticky, so we're not covering them either with the animation MonitorsGroup, and thus there's no need to clone them or we'd end up having two windows painted.
This was causing the shell tray icon window actors (that have no opacity by default but that are override redirect) to show up during the animation as their clone animation is not 0.
The other option would be hide them during the animation phase, but there's no need for this.
Fixes: LP: #2039543
Edited by Marco Trevisan