[Telemetry] Update all clients to use chromium_config.GetTelemetryDir()

tools/chrome_proxy/run_tests

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 """This script runs unit tests of the code in the perf directory.
 
 This script DOES NOT run benchmarks. run_benchmark does that.
 """
 
 import os
 import sys
 
-sys.path.append(os.path.join(os.path.dirname(__file__), os.pardir, 'telemetry'))
+import chrome_proxy_config
+
+sys.path.insert(1, chrome_proxy_config.TELEMETRY_DIR)
 
 from telemetry.testing import unittest_runner
 
-import chrome_proxy_config
-
 
 if __name__ == '__main__':
   sys.exit(unittest_runner.Run(chrome_proxy_config.Config(['integration_tests',
                                                            'live_tests'])))