[telemetry] Change many relative paths to use util.Get*Dir().

tools/telemetry/telemetry/core/browser_credentials.py

Index: tools/telemetry/telemetry/core/browser_credentials.py
diff --git a/tools/telemetry/telemetry/core/browser_credentials.py b/tools/telemetry/telemetry/core/browser_credentials.py
index fadeaa1e0a9df493da91696af54a4e2a1a4708c8..d53c6a80c7bcfd4dd4fdedab1b654877edd86866 100644
--- a/tools/telemetry/telemetry/core/browser_credentials.py
+++ b/tools/telemetry/telemetry/core/browser_credentials.py
@@ -5,6 +5,7 @@ import logging
 import json
 import os
 
+from telemetry.core import util
 from telemetry.core.chrome import facebook_credentials_backend
 from telemetry.core.chrome import google_credentials_backend
 from telemetry.unittest import options_for_unittests
@@ -126,11 +127,8 @@ class BrowserCredentials(object):
                                        page_set.credentials_path)))
       files_to_tweak.append('~/.telemetry-credentials')
 
-      example_credentials_file = (
-        os.path.relpath(
-          os.path.join(
-            os.path.dirname(__file__),
-            '..', 'examples', 'credentials_example.json')))
+      example_credentials_file = os.path.join(
+          util.GetTelemetryDir(), 'examples', 'credentials_example.json')
 
       logging.warning("""
         Credentials for %s were not found. %i pages will not be tested.