chrome_cleaner/os unit tests, part 1: a-f

Also add test_util add extra setup that uses it to the test harness/

Bug: 830892
Change-Id: Iae1bb4323f6a0b25339d13e702135c2a3625c99d
Reviewed-on: https://chromium-review.googlesource.com/1141146
Commit-Queue: Joe Mason <joenotcharles@chromium.org>
Reviewed-by: Chris Sharp <csharp@chromium.org>
Reviewed-by: Penny MacNeil <pennymac@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577240}
32 files changed