autotest/factory: improve message feedback on UI

client/site_tests/factory_WriteGBB/factory_WriteGBB.py

Index: client/site_tests/factory_WriteGBB/factory_WriteGBB.py
diff --git a/client/site_tests/factory_WriteGBB/factory_WriteGBB.py b/client/site_tests/factory_WriteGBB/factory_WriteGBB.py
index 9fe53f76100535257be9d7d35021e6ee7bc9b962..4d742ed61808c68422e91e275d57feeaf5a8e39d 100644
--- a/client/site_tests/factory_WriteGBB/factory_WriteGBB.py
+++ b/client/site_tests/factory_WriteGBB/factory_WriteGBB.py
@@ -14,8 +14,11 @@ class factory_WriteGBB(test.test):
     version = 4
 
     def run_once(self):
-        # If found the HwQual ID in shared_data, identify the component files.
-        probed_hwid = factory.get_shared_data('last_probed_hwid')
+        # We trust previous execution result of HWQual ID probing test: by
+        # hardware_Components(do_probe=True).
+        # If the value was incorrect, it will be detected in the finalization
+        # stage (factory_Finalize, gooftool --finalize => --verify_hwid).
+        probed_hwid = factory.get_shared_data(factory.LAST_PROBED_HWID_NAME)
         if not probed_hwid:
             raise error.TestError(
                     'You need to run this test from factory UI, and have ' +