Refactor FAFT test case by introducing a new method run_faft_step().

BUG=chromium-os:19710
TEST=run_remote_tests.sh --remote=$REMOTE_IP -a \
     "xml_config=$OVERLAY_XML servo_vid=0x18d1 servo_pid=0x5001" control.faft

Change-Id: Icd7763017eec9a0460ce01569b760ec1df983051
Reviewed-on: https://gerrit.chromium.org/gerrit/11510
Reviewed-by: Todd Broch <tbroch@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
7 files changed