Add common.py

We have a 'import common' in config.py but there is not such module.
The common module is suppose to set up sys.path for autotest_lib.*.

BUG=None
TEST=Run `python -c import config` in server/cros/faft/config directory.

Change-Id: Ie90feabf684e5a43b00b396cdb7af90fe9615036
Reviewed-on: https://chromium-review.googlesource.com/208925
Tested-by: Ricky Liang <jcliang@chromium.org>
Reviewed-by: Yusuf Mohsinally <mohsinally@chromium.org>
Reviewed-by: Vic Yang <victoryang@chromium.org>
Commit-Queue: Ricky Liang <jcliang@chromium.org>
diff --git a/server/cros/faft/config/common.py b/server/cros/faft/config/common.py
new file mode 100644
index 0000000..7915157
--- /dev/null
+++ b/server/cros/faft/config/common.py
@@ -0,0 +1,13 @@
+# Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os, sys
+dirname = os.path.dirname(sys.modules[__name__].__file__)
+autotest_dir = os.path.abspath(
+        os.path.join(dirname, os.pardir, os.pardir, os.pardir, os.pardir))
+client_dir = os.path.join(autotest_dir, 'client')
+sys.path.insert(0, client_dir)
+import setup_modules
+sys.path.pop(0)
+setup_modules.setup(base_path=autotest_dir, root_module_name='autotest_lib')