[autotest] move firmware update code from provision_FirmwareUpdate test to CrosHost

Refer to machine_install method, this CL moves the logic needed for repairing
firmware to CrOSHost class. Once servo V3 is ready to update firmware, anothe
CL will be added to enable repair with firmware image.

BUG=chromium:279410
TEST=run test in local setup
test_that 172.22.30.146 provision_FirmwareUpdate  --args "value=falco-release/R36-5832.0.0 servo_host=localhost"
TODO: The test can only be done when servod is running in localhost. bug 381718
needs to be fixed before firmware can be updated using servo runnin beaglebone.
Change-Id: Id1a8d484c231120e6834bc985aaaef9f7ad122e8
Reviewed-on: https://chromium-review.googlesource.com/204451
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
4 files changed