Simplify the test logic by using t.TempDir, t.Chdir, and Chdir to
startPath parent.
Change-Id: Ibe71a8c26b8e54c22eb93510037605b69c67bc7a
Reviewed-on: https://go-review.googlesource.com/c/go/+/606896
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com>