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 
{
    nSizeWithDescendants += modifySize;
    assert(int64_t(nSizeWithDescendants) > 0);
    nModFeesWithDescendants += modifyFee;
    nCountWithDescendants += modifyCount;
    assert(int64_t(nCountWithDescendants) > 0);
}
void CTxMemPoolEntry::UpdateAncestorState(int64_t modifySize, CAmount modifyFee, int64_t modifyCount, int64_t modifySigOps)
{
    nSizeWithAncestors += modifySize;
    assert(int64_t(nSizeWithAncestors) > 0);
    nModFeesWithAncestors += modifyFee;
    nCountWithAncestors += modifyCount;
    assert(int64_t(nCountWithAncestors) > 0);
    nSigOpCostWithAncestors += modifySigOps;
    assert(int(nSigOpCostWithAncestors) >= 0);
}
CTxMemPool::CTxMemPool(CBlockPolicyEstimator* estimator) :
    nTransactionsUpdated(0), minerPolicyEstimator(estimator)
{
    _clear(); 
    
    
    
    nCheckFrequency = 0;
}
bool CTxMemPool::isSpent(const COutPoint& outpoint) const