paygen_payload_lib: Base json on signed_payload_file.

We were dumping the unsigned payload values into payload json
descriptions, even if signing was enabled. We should now used signed
or unsigned values correctly.

BUG=chromium:505094
TEST=Unittests + manually finding md5sums for payload files.

Change-Id: I2630fa1e6a710979fd65f006d9c852de4b3d88cc
Previous-Reviewed-on: https://chromium-review.googlesource.com/282577
(cherry picked from commit bca3be5dbad07a8028546e46b210e18eedf71c17)
Reviewed-on: https://chromium-review.googlesource.com/285155
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
2 files changed