ghost.py: Fix device id.

Fix the device id for ghost.py is still from event_log.DEVICE_ID_PATH,
which is removed in CL:538412

BUG=chromium:711200
TEST=manually

Change-Id: Ic8995610e1516e3bbba6bf9f662c88a1fa0fc94f
Reviewed-on: https://chromium-review.googlesource.com/558853
Commit-Ready: Pi-Hsun Shih <pihsun@chromium.org>
Tested-by: Pi-Hsun Shih <pihsun@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
diff --git a/py/tools/ghost.py b/py/tools/ghost.py
index 57a01a0..f41ae25 100755
--- a/py/tools/ghost.py
+++ b/py/tools/ghost.py
@@ -463,9 +463,8 @@
     # Try factory device id
     try:
       import factory_common  # pylint: disable=unused-variable
-      from cros.factory.test import event_log
-      with open(event_log.DEVICE_ID_PATH) as f:
-        return f.read().strip()
+      from cros.factory.test import testlog_goofy
+      return testlog_goofy.GetDeviceID()
     except Exception:
       pass