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 
{
private:
    uint32_t nCheckFrequency GUARDED_BY(cs); 
    unsigned int nTransactionsUpdated; 
    CBlockPolicyEstimator* minerPolicyEstimator;
    uint64_t totalTxSize;      
    uint64_t cachedInnerUsage; 
    mutable int64_t lastRollingFeeUpdate;
    mutable bool blockSinceLastRollingFeeBump;
    mutable double rollingMinimumFeeRate; 
    void trackPackageRemoved(const CFeeRate& rate) EXCLUSIVE_LOCKS_REQUIRED(cs);
public:
    static const int ROLLING_FEE_HALFLIFE = 60 * 60 * 12; 
    typedef boost::multi_index_container<
        CTxMemPoolEntry,
        boost::multi_index::indexed_by<
            
            boost::multi_index::hashed_unique<mempoolentry_txid, SaltedTxidHasher>,
            
            boost::multi_index::ordered_non_unique<