cros_generate_update_payload: Fix kernel/root extraction.

The payload/root extraction process in cros_generate_update_payload was broken
because it assumed we wanted to extract kernel B and that we didn't need to
patch it. While this is true for new images, old images still need to use
kernel A and to patch it.

BUG=chromium:417072
TEST=Was able to generate/verify a full payload for an old style image
manually.

Change-Id: Ibe007dd0dda5680f9233d44d472e534a7589e4dc
Reviewed-on: https://chromium-review.googlesource.com/220075
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
1 file changed