FAFT: Ignore extracting EC binary on devices without Chrome EC

BUG=chromium:622029
TEST=Ran the firmware_UpdateFirmwareVersion test on a Chromebox

Change-Id: I233eb038b2a3f96eb33cda91d6c9b2890cf37fbc
Reviewed-on: https://chromium-review.googlesource.com/354484
Commit-Ready: Wai-Hong Tam <waihong@google.com>
Tested-by: Wai-Hong Tam <waihong@chromium.org>
Reviewed-by: danny chan <dchan@chromium.org>
diff --git a/server/cros/faft/firmware_test.py b/server/cros/faft/firmware_test.py
index d2f933b..91c4cef 100644
--- a/server/cros/faft/firmware_test.py
+++ b/server/cros/faft/firmware_test.py
@@ -1276,7 +1276,8 @@
             bios_in_work_path = os.path.join(work_path, 'bios.bin')
             ec_in_work_path = os.path.join(work_path, 'ec.bin')
             self.faft_client.bios.dump_whole(bios_in_work_path)
-            self.faft_client.ec.dump_firmware(ec_in_work_path)
+            if self.faft_config.chrome_ec:
+                self.faft_client.ec.dump_firmware(ec_in_work_path)
             self.faft_client.updater.repack_shellball()
 
     def is_kernel_changed(self):