The update_depot_tools script had a line where a call out
to the test operator ([]) wasn't quoting all of the arguments,
leading to errors if a directory had spaces in the name.

R=dnj@chromium.org, phajdan.jr@chromium.org

Bug:
Change-Id: Ie1f5f51891a2582614ed3d9b16375d2ad522360b
Reviewed-on: https://chromium-review.googlesource.com/598427Reviewed-by: Daniel Jacques <dnj@chromium.org>
Commit-Queue: Daniel Jacques <dnj@chromium.org>