Constant organizing.

Move the constants from build_artifact and autoupdate into devserver_constants.
Neaten up XBuddy constants.

BUG=None
TEST=unittests + cbuildbot remote x86-mario

Change-Id: I6fba63f7533dc1349af8e8bdaad07564e4dc0a49
Reviewed-on: https://gerrit.chromium.org/gerrit/63773
Commit-Queue: Joy Chen <joychen@chromium.org>
Reviewed-by: Joy Chen <joychen@chromium.org>
Tested-by: Joy Chen <joychen@chromium.org>
diff --git a/common_util_unittest.py b/common_util_unittest.py
index 34fea31..4354210 100755
--- a/common_util_unittest.py
+++ b/common_util_unittest.py
@@ -13,7 +13,6 @@
 
 import mox
 
-import build_artifact
 import common_util
 import devserver_constants
 
@@ -44,7 +43,7 @@
           build_path, devserver_constants.TEST_IMAGE_FILE), 'w') as f:
           f.write('TEST_IMAGE_FILE')
         with open(os.path.join(
-          build_path, build_artifact.STATEFUL_UPDATE_FILE), 'w') as f:
+          build_path, devserver_constants.STATEFUL_UPDATE_FILE), 'w') as f:
           f.write('STATEFUL_UPDATE_FILE')
         with open(os.path.join(
           build_path, devserver_constants.UPDATE_FILE), 'w') as f: