bug#27091: Request: Toggle scroll bar on each window separately

[Eli Zaretskii]

> Date: Sat, 27 May 2017 10:16:43 +0200
> From: martin rudalics <rudalics@gmx.at>
> 
> Please read section 39.14 Scroll Bars of the Elisp manual which will
> tell you how to control all scroll bar settings for individual windows
> and buffers.

Right.

But it looks like switching buffers in a window whose vertical scroll
bar has been disabled by a call to set-window-scroll-bars restores the
scroll bar, unless I also set the buffer-local variable
vertical-scroll-bars to nil.  What am I doing wrong?