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 
{
    {
        LOCK(cs);
        CAmount &delta = mapDeltas[hash];
        delta += nFeeDelta;
        txiter it = mapTx.find(hash);
        if (it != mapTx.end()) {
            mapTx.modify(it, update_fee_delta(delta));
            
            setEntries setAncestors;
            uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
            std::string dummy;
            CalculateMemPoolAncestors(*it, setAncestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);
            for (txiter ancestorIt : setAncestors) {
                mapTx.modify(ancestorIt, update_descendant_state(0, nFeeDelta, 0));
            }
            
            setEntries setDescendants;
            CalculateDescendants(it, setDescendants);
            setDescendants.erase(it);
            for (txiter descendantIt : setDescendants) {
                mapTx.modify(descendantIt, update_ancestor_state(0, nFeeDelta, 0, 0));
            }
            ++nTransactionsUpdated;
        }
    }
    LogPrintf("PrioritiseTransaction: %s feerate += %s\n", hash.ToString(), FormatMoney(nFeeDelta));
}
void CTxMemPool::ApplyDelta(const uint256 hash, CAmount &nFeeDelta) const