ping_shopfloor: Get download config file from Umpire server

Get resource map from Umpire server, then get download_conf in resource
map as download config file. The ethernet interface is passed from
factory_install.sh to ping_shopfloor.sh since it might not be eth0.

Also, fix the sf_log method so it outputs to stderr. Previously, sf_log
outputs to stdout, and it is only used when ping_shopfloor returns 1.
Now we want to log information when ping_shopfloor returns 0 as well.
Since stdout of ping_shopfloor is used by factory_install.sh when it
returns 0, we need to log to stderr instead.

BUG=chrome-os-partner:25791
TEST=install shim download image from Umpire server.

Change-Id: I7ad33f1938f8d51f694fa377f42a578d899ae6b0
Reviewed-on: https://chromium-review.googlesource.com/202902
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Rong Chang <rongchang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
Commit-Queue: Cheng-Yi Chiang <cychiang@chromium.org>
2 files changed