[PowerProfiler] Make sure correct version of pySerial is imported with monsoon profiler.

tools/telemetry/telemetry/core/util.py

 # Copyright 2012 The Chromium 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 glob
 import imp
 import inspect
 import logging
 import os
 import socket
 import sys
@@ skipping 20 matching lines @@
 def GetUnittestDataDir():
   return os.path.join(GetTelemetryDir(), 'unittest_data')
 
 
 def GetChromiumSrcDir():
   return os.path.normpath(os.path.join(GetTelemetryDir(), os.pardir, os.pardir))
 
 
 def AddDirToPythonPath(*path_parts):
   path = os.path.abspath(os.path.join(*path_parts))
-  if os.path.isdir(path) and path not in sys.path:
-    sys.path.append(path)
+  if os.path.isdir(path):
+    if path in sys.path:
+      sys.path.remove(path)
+    sys.path.insert(0, path)
 
 _counter = [0]
 def _GetUniqueModuleName():
   _counter[0] += 1
   return "page_set_module_" + str(_counter[0])
 
 def GetPythonPageSetModule(file_path):
   return imp.load_source(_GetUniqueModuleName(), file_path)
 
 
@@ skipping 105 matching lines @@
   """
   name, ext = os.path.splitext(base_name)
   assert ext == '', 'base_name cannot contain file extension.'
   index = 0
   while True:
     output_name = '%s_%03d' % (name, index)
     if not glob.glob(output_name + '.*'):
       break
     index = index + 1
   return output_name