When dynamic workspaces are used, we pick up an existing NUMBER_OF_DESKTOP
hint in meta_screen_init_workspaces() to properly restore workspaces
on restart. Unconditionally setting that hint to 1 *before* reading it
breaks that, and we end up shifting all windows to the first workspace.
This reverts commit 8532b102909e09e1e0fdbd7f2701a7c40de1af5f.
https://bugzilla.gnome.org/show_bug.cgi?id=760651