servo: Add back the route to retrieve serials, like servo-micro and CCD

The controls, like 'ccd_serialname', 'servo_micro_for_soraka_serialname',
are used by flash_ec script to retrieve the serials on servo v4, which
connects to multiple servo-micros or CCD.

Add back the route. Will refactor it in a better way later.

BUG=b:67431336
TEST=Ran servod and tested the controls 'ccd_serialname' and
'servo_micro_for_soraka_serialname'.

Change-Id: I430da66101696a41251aca8346a37d4b6b42ef56
Reviewed-on: https://chromium-review.googlesource.com/703686
Commit-Ready: Wai-Hong Tam <waihong@google.com>
Tested-by: Wai-Hong Tam <waihong@google.com>
Reviewed-by: Ruben Rodriguez Buchillon <coconutruben@chromium.org>
diff --git a/servo/servo_server.py b/servo/servo_server.py
index bfe5c1c..90ef7f0 100755
--- a/servo/servo_server.py
+++ b/servo/servo_server.py
@@ -962,6 +962,13 @@
       HwDriverError: Error occurred while using drv
     """
     self._logger.debug("name(%s)" % (name))
+    # This route is to retrieve serialnames on servo v4, which
+    # connects to multiple servo-micros or CCD, like the controls,
+    # 'ccd_serialname', 'servo_micro_for_soraka_serialname', etc.
+    # TODO(aaboagye): Refactor it.
+    if 'serialname' in name:
+        return self.get_serial_number(name.split('serialname')[0].strip('_'))
+
     (param, drv) = self._get_param_drv(name)
     try:
       val = drv.get()