Don't add windows to overlay workspaces when overlay is being exited.

When a window is added while overlay is being exited (e.g. because
some application was launched), we don't want to add that window to
the workspace's window clones. Previously, the window clone was added
and an animation to place the windows to their overlay workspace view
positions was triggered, which resulted in the wrong animation being
shown and an abrupt change in window positions when the actual workspace
was shown.

Add a boolean argument to two _positionWindows() calls that were missing
an argument.