Have "bot_update.py" export the failing patch body in its JSON. Have the
recipe actually emit the patch body in the "Patch Failure" step instead
of the "bot_update" step, and remove the "Patch Failure" step's
indirection to the "bot_update" step for patch failure.

This will provide a more straightforward user interface: the red step
that says "Patch Failure" now includes the details of the patch failure!

BUG=chromium:710477
TEST=expectations

Change-Id: I6ad305f0b972de89e4f0b5eb70edf41980447abd
Reviewed-on: https://chromium-review.googlesource.com/475950
Commit-Queue: Daniel Jacques <dnj@chromium.org>
Reviewed-by: Ryan Tseng <hinoka@chromium.org>