A FAFT test of closing lid during firmware screens.

This test requires a USB disk plugged-in, which contains a Chrome OS test
image (built by "build_image --test"). On runtime, this test triggers
four firmware screens (developer, remove, insert, and yuck screens), and
then closes the lid in order to power the machine down.

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

Change-Id: I7b6be27b9d6051b1b978d47228027ce065e792fe
Reviewed-on: https://gerrit.chromium.org/gerrit/13452
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
diff --git a/server/cros/faftsequence.py b/server/cros/faftsequence.py
index 38270a3..819fa72 100644
--- a/server/cros/faftsequence.py
+++ b/server/cros/faftsequence.py
@@ -584,7 +584,8 @@
         """
         assert len(from_magic) == 8
         assert len(to_magic) == 8
-        kernel_part = self._join_part(usb_dev, '2')
+        # USB image only contains one kernel.
+        kernel_part = self._join_part(usb_dev, self.KERNEL_MAP['a'])
         read_cmd = "sudo dd if=%s bs=8 count=1 2>/dev/null" % kernel_part
         current_magic = utils.system_output(read_cmd)
         if current_magic == to_magic: