Bug 1175545 - Dont process alt-svc on 421 r=hurley

netwerk/protocol/http/nsHttpChannel.cpp

@@ -1375,7 +1375,7 @@ nsHttpChannel::ProcessResponse()
     // happen after OnExamineResponse.
     if (!mTransaction->ProxyConnectFailed() && (httpStatus != 407)) {
         SetCookie(mResponseHead->PeekHeader(nsHttp::Set_Cookie));
-        if (httpStatus < 500) {
+        if ((httpStatus < 500) && (httpStatus != 421)) {
             ProcessAltService();
         }
     }