[autotest] Add unit test coverage for Offloader constructor.

This adds coverage for gs_offloader.Offloader constructor in
preference to testing gs_offloader.parse_options() directly.
This has the advantage of killing two birds with one stone;
the disadvantage is that bugs in either option parsing or the
constructor can't be distinguished without debugging.

BUG=None
TEST=Run the new unit tests
DEPLOY=gs_offloader

Change-Id: I29a40aa608623958076a79d5571890a6ce08d205
Reviewed-on: https://chromium-review.googlesource.com/200630
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Alex Miller <milleral@chromium.org>
Commit-Queue: Richard Barnette <jrbarnette@chromium.org>
1 file changed