bug#22338: 25.0.50; deactivate-mark regression

[Leo Liu]

1. Emacs -q
2. Open a file and mark an active region
3. (revert-buffer nil t t)

The mark is still active after the buffer revert. This isn't the case
for emacs 24.5.

The trouble is if the file has changed on disk (e.g. by another process
such as vim), the mark is still active after the revert.

Leo