[autotest] Add firmware repair to CrOSHost repair logic.

This is to help to revoery duts failed in FAFT.

DUT to be repaired by firmware_repair will need to be in pool:faft-test.
The board will also need to have an entry in stable_version table, e.g.
daisy_spring/firmware: daisy_spring-firmware/R41-6588.127.0

BUG=chromium:279410,chromium:535456
TEST=unititest, local run

Change-Id: I85edee5cef2093fefecfd5e9db89848d16fc839e
Reviewed-on: https://chromium-review.googlesource.com/305290
Commit-Ready: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Wai-Hong Tam <waihong@chromium.org>
3 files changed