When managing window, we queue showing the window.
Under wayland, if we commit surface quickly enough,
the showing is unqueued and commit procedure takes care
of mapping and placing the window. In the oposite case,
queue is processed before client sets all we need and
then we have wrong size of window, which leads to broken placement.
Therefore force placement in queue only if the window should already
be mapped. If it is not mapped, we don't care where it is anyway.
https://bugzilla.gnome.org/show_bug.cgi?id=751887
99c0b82b15