Get rid of image_burner_tester

and while here, fix two missing returns.

BUG=chromium:221781
TEST=image burner unittests; verified chrome://imageburner not broken

Change-Id: Ie185d7c692b2da4584954953ab4b681c487c3415
Reviewed-on: https://gerrit.chromium.org/gerrit/58459
Reviewed-by: Elly Jones <ellyjones@chromium.org>
Commit-Queue: Toni Barzic <tbarzic@chromium.org>
Tested-by: Toni Barzic <tbarzic@chromium.org>
3 files changed