Fix bugs in autotest firmware_updateECBin

Fix the following bugs:
1. Some methods do not follow the new naming style.
2. New_ec_checker failed in step 3.
3. In some steps, delay of waiting for dev screen is not enough (caused by
    software sync) during ecfw_act=RW.

BUG=chrome-os-partner:35902
TEST=run firmware_updateECBin test

Change-Id: I6a0bad694c455b7bde8de9726a2e3bcf0bfeda0f
Reviewed-on: https://gerrit.chromium.org/gerrit/39459
Reviewed-by: Tom Wai-Hong Tam <waihong@chromium.org>
Commit-Ready: Chun-Ting Chang <ctchang@chromium.org>
Tested-by: Chun-Ting Chang <ctchang@chromium.org>
diff --git a/client/cros/faft_client.py b/client/cros/faft_client.py
index 5242f60..feaaacf 100755
--- a/client/cros/faft_client.py
+++ b/client/cros/faft_client.py
@@ -456,7 +456,7 @@
         blob = self._ec_image.get_section_body('rw')
         self._bios_handler.set_section_ecbin(section, blob,
                                              write_through=True)
-        self.set_firmware_flags(section, flags)
+        self._bios_set_preamble_flags(section, flags)
 
 
     def _bios_dump_whole(self, bios_path):