After discussing offline, we feel like the reading/writing HWID processes is not related to HWID "V3" features.  So we prefer moving these two methods in gooftool module and in hwid tool, it just calls the method in gooftool to fulfill the task.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/factory/+/c376541244ad282d5678173894982a50bec3b051

commit c376541244ad282d5678173894982a50bec3b051
Author: Yong Hong <yhong@chromium.org>
Date: Tue Feb 06 20:21:02 2018

hwid: Deletages the HWID reading/writing function to gooftool.

Both reading/writing the HWID string from/to firmware GBB is not
related to the HWID v3 framework, so this CL removes the related
functions in `cros.factory.hwid.v3.hwid_utils` and lets `hwid read`
and `hwid write` command just delegate the real work to gooftool.

TEST=manual test
BUG= chromium:769653 

Change-Id: I6f45003ae7b143badbfeb0db8089db74c456cb05
Reviewed-on: https://chromium-review.googlesource.com/844439
Commit-Ready: Yong Hong <yhong@google.com>
Tested-by: Yong Hong <yhong@google.com>
Reviewed-by: Yilun Lin <yllin@chromium.org>

[modify] https://crrev.com/c376541244ad282d5678173894982a50bec3b051/py/hwid/v3/hwid_cmdline.py
[modify] https://crrev.com/c376541244ad282d5678173894982a50bec3b051/py/gooftool/commands.py
[modify] https://crrev.com/c376541244ad282d5678173894982a50bec3b051/py/gooftool/core.py
[modify] https://crrev.com/c376541244ad282d5678173894982a50bec3b051/py/hwid/v3/hwid_utils.py