Fix and enable the PAC fetcher NoCache test on Android

The NoCache test for the PAC fetcher verifies that an attempt to
fetch a PAC script fails once the server is killed, thus assuring
that PAC files are not cached.

Due to the device-server / port forwarding layout of running 
gtests on Android, the specific error being returned by the 
fetch attempt is "Connection reset by peer" rather than 
"Connection refused". This patch takes this into consideration.

BUG=161763

Review URL: https://chromiumcodereview.appspot.com/11412070

git-svn-id: http://src.chromium.org/svn/trunk/src/build@168805 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

android/gtest_filter/net_unittests_disabled

@@ -11,7 +11,6 @@ HTTPSEVCRLSetTest.FreshCRLSet
 HTTPSRequestTest.ClientAuthTest
 HTTPSRequestTest.ResumeTest
 HTTPSRequestTest.SSLSessionCacheShardTest
-ProxyScriptFetcherImplTest.NoCache
 PythonUtils.PythonRunTime
 TransportSecurityStateTest.ValidPinsHeadersSHA1
 TransportSecurityStateTest.ValidPinsHeadersSHA256