Change in vc-git ls-files-unknown makes emacs hang

[Filipp Gunbin]

Hi, this commit makes Emacs hang and become unusable, this happens when
loading the desktop.  Quitting doesn't unfreeze, so I can't get the
backtrace.  I'm on macOS, tty emacs.

commit 1a2445c45f901d9d939f2992dd8e616e5d7cb9ca
Author: Andrii Kolomoiets <address@hidden>
Date:   Tue Dec 17 01:49:34 2019 +0200
  Make ls-files-unknown only return proper files, not directories

I can't tell the reason of the hang, but reverting it helps.

Andrii, could you please look into it, or revert?

Thanks.
Filipp