bug#31764: 26.1; Point in VC change log is not centered as documented

[Eli Zaretskii]

> From: Noam Postavsky <npostavs@gmail.com>
> Cc: carlosjosepita@gmail.com,  31764@debbugs.gnu.org
> Date: Mon, 11 Jun 2018 20:10:17 -0400
> 
> Looks like a matter of timing, if I add a (sit-for 1) to beginning of
> vc-exec-after (or use edebug), then I can reproduce on Windows too.
> Adding a save-excursion seems to fix it.

Then please push to the emacs-26 branch, and thanks.