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 
if (!g_chainstate.RewindBlockIndex(params)) {
        return false;
    }
    if (chainActive.Tip() != nullptr) {
        
        
        
        CValidationState state;
        if (!FlushStateToDisk(params, state, FlushStateMode::ALWAYS)) {
            LogPrintf("RewindBlockIndex: unable to flush state to disk (%s)\n", FormatStateMessage(state));
            return false;
        }
    }
    return true;
}
void CChainState::UnloadBlockIndex() {