factory_install: Save Omaha server URL into /usr/local/etc/lsb-factory

To help integrating shop floor system (and any other system using mini-omaha
server) into factory flow, we should always record Omaha server URL after
factory installation.

BUG=chrome-os-partner:6911
TEST=Manually performed factory installation and found FACTORY_OMAHA_URL in
     /usr/local/etc/lsb-factory on DUT.

Change-Id: I233fddd0e7b8f9a788a5d553bca65e49a7c07052
Reviewed-on: https://gerrit.chromium.org/gerrit/13559
Reviewed-by: Tammo Spalink <tammo@chromium.org>
Commit-Ready: Hung-Te Lin <hungte@chromium.org>
Tested-by: Hung-Te Lin <hungte@chromium.org>
1 file changed