overlord: add unittest for sysutils

Add unittest for sysutils and fix a GetProcessWorkingDirectory for
Darwin.

BUG=none
TEST=go test

Change-Id: Ic2535810fa9f44f24bbcedd7919de5fc551b4f24
Reviewed-on: https://chromium-review.googlesource.com/344445
Commit-Ready: Wei-Ning Huang <wnhuang@chromium.org>
Tested-by: Wei-Ning Huang <wnhuang@chromium.org>
Reviewed-by: Wei-Han Chen <stimim@chromium.org>
2 files changed