shell/app: Don't move all workspace windows to their startup workspace

Windows from some applications, such as guake, are created as showing on all workspaces. When these windows are put on the workspaces via set_workspace_state() during construction, the first time the window is added to a workspace in the loop triggers the shell app tracker which then tries to move the window to its startup workspace. This makes the window unsticky which triggers another set_workspace_state() which tries to remove the window from all workspaces, but currently it is only on the first one and then adds it to the startup workspace. Once that is finished, the first set_workspace_state() continues adding the window to the remaining workspaces, despite the window now no longer having on_all_workspaces set to true.

When the window is now unmanaged, the window according to its internal state is only found on the startup workspace, so it will only be removed from that. This causes the assertion to fail that checks that the window is no longer present on any workspace after this.

Fixes #4720 (closed)