Fix testAboutAppCacheTab by replacing External 500 error URL to working URL.

chrome/test/functional/PYAUTO_TESTS

 # Copyright (c) 2011 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 file lists the pyauto tests that run as a part of the functional test
 # suite.
 #
 # Tests can be enabled on a per-platform basis. Tests not listed here will
 # not be run.
 #
@@ skipping 95 matching lines @@
       # crbug.com/47935
       '-popups.PopupsTest.testBlockedPopupNotShowInHistory',
       # crbug.com/83827
       '-popups.PopupsTest.testUnblockedPopupAddedToOmnibox',
       # crbug.com/85600
       '-prefs.PrefsTest.testNavigationStateOnSessionRestore',
       # Flaky browser crash.  crbug.com/99944
       '-search_engines.SearchEnginesTest.testDefaultSearchEngines',
       # Flaky: crbug.com/67851
       '-special_tabs.SpecialTabsTest.testAboutDNSTab',
-      # crbug.com/102517 -- external webpage throws 500
-      '-special_tabs.SpecialTabsTest.testAboutAppCacheTab',
       # crbug.com/95140
       '-translate.TranslateTest.testGoBackAndForwardToTranslatePage',
       # crbug.com/86524
       '-plugins.PluginsTest.testAllowPluginException',
       # crbug.com/85307
       '-plugins.PluginsTest.testKillAndReloadAllPlugins',
       # crbug.com/88574
       '-special_tabs.SpecialTabsTest.testSpecialURLTabs',
       # crbug.com/88593
       '-sync.SyncTest.testPersonalStuffSyncSection',
@@ skipping 492 matching lines @@
 
   # HTML5 media functional tests.
   'AV_FUNC': {
      'linux': [
        'media.media_event_simple_action',
        'media.media_event_simple_test',
        'media.media_event_track',
      ],
   },
 }