kcmkwin/rules: Fix suggested values for virtual desktops rule

If the virtual desktops rule is created, only the last virtual desktop
the window is on is going to be checked.

With this, all virtual desktops that the window is currently on will be
checked.

Technically, it's an api breaking change, but the window rules kcm is
the primary user of queryWindowInfo() so I don't think it's a big deal.


(cherry picked from commit 66badd90)