Reported here: https://github.com/bitcoin/bitcoin/pull/10244#issuecomment-378035305

Travis log here: https://travis-ci.org/bitcoin/bitcoin/jobs/361243719#L2810

Note the JSON exception:

```
test_framework.authproxy.JSONRPCException: The mempool was not loaded yet (-1) 
```

That exception was introduced here: https://github.com/bitcoin/bitcoin/commit/cb1e319fe9e198c9c5cf5236fe9af5a3d748b9e8#diff-a0c8f511d90e83aa9b5857e819ced344R1617

cc @jtimon 
StopRPC();
    StopHTTPServer();
    for (const auto& client : interfaces.chain_clients) {
        client->flush();
    }
    StopMapPort();
    
    
    if (peerLogic) UnregisterValidationInterface(peerLogic.get());
    if (g_connman) g_connman->Stop();
    if (g_txindex) g_txindex->Stop();
    StopTorControl();
    
    
    threadGroup.interrupt_all();
    threadGroup.join_all();
    
    
    peerLogic.reset();
    g_connman.reset();
    g_banman.reset();
    g_txindex.reset();
    if (g_is_mempool_loaded && gArgs.GetArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)) {
        DumpMempool();
    }
    if (fFeeEstimatesInitialized)
    {
        ::feeEstimator.FlushUnconfirmed();
        fs::path est_path = GetDataDir() / FEE_ESTIMATES_FILENAME;
        CAutoFile est_fileout(fsbridge::fopen(est_path, "wb"), SER_DISK, CLIENT_VERSION);