Fix commit_ts test suite for systems with coarse timestamp granularity.

Noah Misch <noah@leadboat.com>

Commit: 0916eba131530b296f86137759a32f66ffedff7b
Author: Noah Misch <noah@leadboat.com>
Date: 2014-12-16T01:56:09Z
Releases: 9.5.0
Fix commit_ts test suite for systems with coarse timestamp granularity.

Noticed on a couple of Windows configurations.

Petr Jelinek, reviewed by Michael Paquier.

Files