factory_installer: force updating firmware in factory install mode.

Factory test images (and install shims) are configured with
"leave_firmware_alone" because they may contain firmware blobs that are
different from the real version to install.

So we have to explicitly assign the "force" flag when factory installer is
trying to update the firmware to the assigned version (by make_factory_package
--firmwareupdate).

BUG=chrome-os-partner:3152
TEST=built a factory install shim, then
     make_factory_package --... --firmware_updater=xxx,
     and see firmware update messages on verbose progress log.

Change-Id: I913957e0abd2acdd1191f5c4c98c352eed50bf95

[email protected],[email protected]

Review URL: http://codereview.chromium.org/6806001
diff --git a/memento_updater.sh b/memento_updater.sh
index 56f1bcc..4bc8e1c 100755
--- a/memento_updater.sh
+++ b/memento_updater.sh
@@ -333,7 +333,8 @@
 if [ "${FLAGS_force_track}" = "firmware-channel" ]; then
   log execute firmware-install script
   INSTALL_SCRIPT="${FLAGS_dst_partition}"
-  /bin/sh "${INSTALL_SCRIPT}" --factory 2>&1 | cat >> "$MEMENTO_AU_LOG"
+  /bin/sh "${INSTALL_SCRIPT}" --force --mode=factory_install 2>&1 |
+    cat >> "$MEMENTO_AU_LOG"
   [ "${PIPESTATUS[*]}" = "0 0" ]
   FIRMWAREUPDATE_RETURN_CODE=$?
   abort_update_if_cmd_failed_long "$FIRMWAREUPDATE_RETURN_CODE" \