gclient-new-workdir.py should work on systems not supporting reflink now.

Bug: 728903, 721585
Change-Id: I1385c4281bbf61d4ccae64c3595a39972fbe9d9e
Reviewed-on: https://chromium-review.googlesource.com/522232
Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>