Factory install shim: Fix the bug when trying to bring up network

Not every kernel modules can be loaded (mobprobe) successfully in
factory shim environment. We want to load only USB ethernet modules
for network bringup.

BUG=chromium:662313
TEST=build install shim and open shell

Change-Id: I38227a65f8dab3f9456308710fcd56c7be997fb2
Reviewed-on: https://chromium-review.googlesource.com/407717
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: Chun-Tsen Kuo <chuntsen@chromium.org>
Commit-Queue: Chun-Tsen Kuo <chuntsen@chromium.org>
1 file changed