When a pass of CreateTransaction fails to select enough bitcoin to meet the nFeeNeeded the next pass through may select a far smaller collection of inputs.  Currently it will continue to use the old fee amount based on the larger set of inputs, which can cause a non-trivial over-payment.

This may be the cause of the behavior reported here: https://www.reddit.com/r/Bitcoin/comments/5ltw5n/bitcoin_core_v0131_sends_enormously_high_fee/

Long ago fixing this was tricky due to a catch-22 between signing the transaction and knowing how much fee was required.  But after #9465 the whole algorithm will run using a dummy signature, so when there is already a change output fixing up the fee after finding a sufficient transaction should be a matter of a ~2 line change.

{
    return std::max(minTxFee.GetFee(nTxBytes), ::minRelayTxFee.GetFee(nTxBytes));
}
CAmount CWallet::GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarget, const CTxMemPool& pool)
{
    
    CAmount nFeeNeeded = payTxFee.GetFee(nTxBytes);
    
    if (nFeeNeeded == 0) {
        int estimateFoundTarget = nConfirmTarget;
        nFeeNeeded = pool.estimateSmartFee(nConfirmTarget, &estimateFoundTarget).GetFee(nTxBytes);
        
        if (nFeeNeeded == 0)
            nFeeNeeded = fallbackFee.GetFee(nTxBytes);
    }
    
    nFeeNeeded = std::max(nFeeNeeded, GetRequiredFee(nTxBytes));
    
    if (nFeeNeeded > maxTxFee)
        nFeeNeeded = maxTxFee;
    return nFeeNeeded;
}
DBErrors CWallet::LoadWallet(bool& fFirstRunRet)