Refactor site_power_status, power_strip modules into client/cros.

client/site_tests/power_StatsUSB/power_StatsUSB.py

 # Copyright (c) 2010 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 logging, time
 from autotest_lib.client.bin import test
-from autotest_lib.client.common_lib import site_power_status
+from autotest_lib.client.cros import power_status
 
 
 class power_StatsUSB(test.test):
     version = 1
 
 
     def run_once(self, test_time=60):
-        usb = site_power_status.USBSuspendStats()
+        usb = power_status.USBSuspendStats()
 
         # get USB percent active since boot
         stats = usb.refresh(incremental=False)
         logging.info('USB active time since boot: %.2f%%', stats)
 
         # sleep for some time
         time.sleep(test_time)
 
         # get USB percent active during the test time
         stats = usb.refresh()
         logging.info('USB active time in the last %d seconds: %.2f%%',
                      test_time, stats)