fake_omaha: add a nebraska wrapper to handle update requests

This CL adds a new class that lets gs_archive_server handle the update
RPC requests from DUTs. This class is essentially a wrapper for
nebraska.py. This class also downloads the nebraska properties file into
the /tmp directory and passes that directory to nebraska.

BUG=chromium:1078188
TEST=Ran update_engine_client --omaha_url=<url> --follow on DUT. Output
and exact command can be found at http://gpaste/5083884435800064.

Cq-Depend: chrome-internal:3141905
Change-Id: Ia8559c698e84f15540c4814d14cabafe731e5f55
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2258234
Tested-by: Sanika Kulkarni <sanikak@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Congbin Guo <guocb@chromium.org>
Commit-Queue: Sanika Kulkarni <sanikak@chromium.org>
Auto-Submit: Sanika Kulkarni <sanikak@chromium.org>
2 files changed