chromite: make gsutil accept a user to create cache dir.

This CL is used for devserver package on DUT calling gsutil in chromite.
In this condition, devserver could pass an argument user to create
cache_dir, to avoid the case that 'root user cannot create cache dir'.

BUG=chromium:698304
TEST=emerge chromite to local moblab DUT, call devserver to provision
it. Ran cros flash ssh://. Ran cbuildbot/run_unittest.

Change-Id: Icb23297bc350620a751f1146bcab969f72ff83b1
Reviewed-on: https://chromium-review.googlesource.com/457859
Commit-Ready: Xixuan Wu <xixuan@chromium.org>
Tested-by: Xixuan Wu <xixuan@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Michael Tang <ntang@chromium.org>
(cherry picked from commit 5f625f556cb38a5958f00f73fbbea20a06bf6ac5)
Reviewed-on: https://chromium-review.googlesource.com/477438
Reviewed-by: Keith Haddow <haddowk@chromium.org>
Reviewed-by: Xixuan Wu <xixuan@chromium.org>
Commit-Queue: Keith Haddow <haddowk@chromium.org>
Commit-Queue: Michael Tang <ntang@chromium.org>
Tested-by: Keith Haddow <haddowk@chromium.org>
Tested-by: Michael Tang <ntang@chromium.org>
Trybot-Ready: Michael Tang <ntang@chromium.org>
4 files changed