Python doesn't guarantee that the file created by tempfile.NamedTemporaryFile can be opened by multiple programs at once.
This is the case on Windows, so we need to close the temporary PID file and only then pass it to Git.

Bug: 962263
Change-Id: Idf4a36b33ce06d7ab06453c20a690622179aef58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1608560
Auto-Submit: Raul Tambre <raul@tambre.ee>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Raul Tambre <raul@tambre.ee>