meta_workspace_manager_override_workspace_layout is implemented by
calling meta_workspace_manager_update_workspace_layout which
respects the workspace_layout_overridden flag. After the first call
to meta_workspace_manager_override_workspace_layout all subsequent
calls fail silently.
Reset workspace_layout_overridden to FALSE before calling
meta_workspace_manager_update_workspace_layout.
https://gitlab.gnome.org/GNOME/mutter/issues/270