hwid: Moves exported interfaces into `hwid_utils` module.

This CL moves exported interfaces and constants from
`cros.factory.hwid.v3.common` to `cros.factory.hwid.v3.hwid_utils`.

The module `cros.factory.hwid.v3.common` should contain only HWID
framework internal used classes, and all the exported interfaces should
be located in `cros.factory.hwid.v3.hwid_utils`.

TEST=make test
BUG=chromium:797645

Change-Id: I4ff8376aa4f6b079431d8d173f847e22fffe085e
Reviewed-on: https://chromium-review.googlesource.com/844296
Commit-Ready: Yong Hong <yhong@google.com>
Tested-by: Yong Hong <yhong@google.com>
Reviewed-by: Yong Hong <yhong@google.com>
diff --git a/py/gooftool/commands.py b/py/gooftool/commands.py
index ab0f496..5f95245 100755
--- a/py/gooftool/commands.py
+++ b/py/gooftool/commands.py
@@ -28,7 +28,6 @@
 from cros.factory.gooftool.core import Gooftool
 from cros.factory.gooftool import crosfw
 from cros.factory.gooftool import report_upload
-from cros.factory.hwid.v3 import common
 from cros.factory.hwid.v3 import hwid_utils
 from cros.factory.probe.functions import chromeos_firmware
 from cros.factory.test.env import paths
@@ -118,7 +117,7 @@
 
 _hwdb_path_cmd_arg = CmdArg(
     '--hwdb_path', metavar='PATH',
-    default=common.DEFAULT_HWID_DATA_PATH,
+    default=hwid_utils.DEFAULT_HWID_DATA_PATH,
     help='Path to the HWID database.')
 
 _hwid_status_list_cmd_arg = CmdArg(