Running on recent master, commit f1dbf92ff0475a01d20170ea422c1d086acbbc57

If I run:
```
test/functional/feature_fee_estimation.py --randomseed 108574360997204915
```

I get:
```
2020-12-19T20:14:06.175000Z TestFramework (INFO): Initializing test directory /tmp/bitcoin_func_test_bcwexp78
2020-12-19T20:14:07.738000Z TestFramework (INFO): This test is time consuming, please be patient
2020-12-19T20:14:07.738000Z TestFramework (INFO): Splitting inputs so we can generate tx's
2020-12-19T20:14:10.870000Z TestFramework (INFO): Finished splitting
2020-12-19T20:14:12.104000Z TestFramework (INFO): Will output estimates for 1/2/3/6/15/25 blocks
2020-12-19T20:14:12.104000Z TestFramework (INFO): Creating transactions and mining them with a block size that can't keep up
2020-12-19T20:14:15.879000Z TestFramework (INFO): Creating transactions and mining them at a block size that is just big enough
2020-12-19T20:14:21.104000Z TestFramework (ERROR): Assertion failed
Traceback (most recent call last):
  File "/home/sdaftuar/ccl-bitcoin/2020-12-latest-master/test/functional/test_framework/test_framework.py", line 126, in main
    self.run_test()
  File "test/functional/feature_fee_estimation.py", line 256, in run_test
    check_estimates(self.nodes[1], self.fees_per_kb)
  File "test/functional/feature_fee_estimation.py", line 140, in check_estimates
    check_smart_estimates(node, fees_seen)
  File "test/functional/feature_fee_estimation.py", line 130, in check_smart_estimates
    % (feerate, last_feerate))
AssertionError: Estimated fee (0.000565) larger than last fee (0.000479) for lower number of confirms

```
}
    
    
    
    nBestSeenHeight = nBlockHeight;
    
    feeStats->ClearCurrent(nBlockHeight);
    shortStats->ClearCurrent(nBlockHeight);
    longStats->ClearCurrent(nBlockHeight);
    
    feeStats->UpdateMovingAverages();
    shortStats->UpdateMovingAverages();
    longStats->UpdateMovingAverages();
    unsigned int countedTxs = 0;
    
    for (const auto& entry : entries) {
        if (processBlockTx(nBlockHeight, entry))
            countedTxs++;
    }
    if (firstRecordedHeight == 0 && countedTxs > 0) {
        firstRecordedHeight = nBestSeenHeight;
        LogPrint(BCLog::ESTIMATEFEE, "Blockpolicy first recorded height %u\n", firstRecordedHeight);
    }
    LogPrint(BCLog::ESTIMATEFEE, "Blockpolicy estimates updated by %u of %u block txs, since last block %u of %u tracked, mempool map size %u, max target %u from %s\n",
             countedTxs, entries.size(), trackedTxs, trackedTxs + untrackedTxs, mapMemPoolTxs.size(),
             MaxUsableEstimate(), HistoricalBlockSpan() > BlockSpan() ? "historical" : "current");
    trackedTxs = 0;
    untrackedTxs = 0;
}
CFeeRate CBlockPolicyEstimator::estimateFee(int confTarget) const