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.

{
    CAmount nTotal = 0;
    {
        LOCK2(cs_main, cs_wallet);
        for (map<uint256, CWalletTx>::const_iterator it = mapWallet.begin(); it != mapWallet.end(); ++it)
        {
            const CWalletTx* pcoin = &(*it).second;
            if (!pcoin->IsTrusted() && pcoin->GetDepthInMainChain() == 0 && pcoin->InMempool())
                nTotal += pcoin->GetAvailableCredit();
        }
    }
    return nTotal;
}
CAmount CWallet::GetImmatureBalance() const
{
    CAmount nTotal = 0;
    {
        LOCK2(cs_main, cs_wallet);
        for (map<uint256, CWalletTx>::const_iterator it = mapWallet.begin(); it != mapWallet.end(); ++it)
        {
            const CWalletTx* pcoin = &(*it).second;
            nTotal += pcoin->GetImmatureCredit();
        }
    }
    return nTotal;
}
CAmount CWallet::GetWatchOnlyBalance() const