nebraska: Distinguish between platform and DLC request

We need this difference to respond to an update/install with parameters
that should only be available for platform vs DLC APP tags in the
response. For example, requesting a rollback should only return response
for platform App request. Same as what Omaha/GE will do.

BUG=chromium:999047
TEST=nebraska_unittest.py

Change-Id: Ied173e71407fec49b163818c7ce1cb2401c6bd85
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/1951505
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Amin Hassani <ahassani@chromium.org>
2 files changed