I was messing around with min relay policies and found that under certain circumstances the mempool will accept things, then not relay to any peers.

Example made using wallet:
Transaction of size 6195, fee of 619 satoshis, minrelay of 100 satoshis per kvB. Mempool logic allows it:

```
        // No transactions are allowed below minRelayTxFee except from disconnected blocks
        if (!bypass_limits && nModifiedFees < ::minRelayTxFee.GetFee(nSize)) {
            return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "min relay fee not met", false, strprintf("%d < %d", nModifiedFees, ::minRelayTxFee.GetFee(nSize)));
        }
```
and lets it into mempool

but in net_processing.cpp:

```
                    if (filterrate && txinfo.feeRate.GetFeePerK() < filterrate) {
                        continue;
                    }
```
this gets hit because the computed feerate is insufficient(printing I added):
```
0.00000099 BTC/kB
```

I'm not super at arithmetic so I'm opening this up in case someone has an easy fix. 

let me also get a reproducible test failure with this...
{
    setEntries setAncestors;
    uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
    std::string dummy;
    CalculateMemPoolAncestors(entry, setAncestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy);
    return addUnchecked(entry, setAncestors, validFeeEstimate);
}
void CTxMemPool::UpdateChild(txiter entry, txiter child, bool add)
{
    setEntries s;
    if (add && mapLinks[entry].children.insert(child).second) {
        cachedInnerUsage += memusage::IncrementalDynamicUsage(s);
    } else if (!add && mapLinks[entry].children.erase(child)) {
        cachedInnerUsage -= memusage::IncrementalDynamicUsage(s);
    }
}
void CTxMemPool::UpdateParent(txiter entry, txiter parent, bool add)