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.

{
        CWalletTx& wtx = *(item.second);
        LOCK(mempool.cs);
        CValidationState state;
        wtx.AcceptToMemoryPool(maxTxFee, state);
    }
}
bool CWalletTx::RelayWalletTransaction(CConnman* connman)
{
    assert(pwallet->GetBroadcastTransactions());
    if (!IsCoinBase() && !isAbandoned() && GetDepthInMainChain() == 0)
    {
        CValidationState state;
        
        if (InMempool() || AcceptToMemoryPool(maxTxFee, state)) {
            LogPrintf("Relaying wtx %s\n", GetHash().ToString());
            if (connman) {
                CInv inv(MSG_TX, GetHash());
                connman->ForEachNode([&inv](CNode* pnode)
                {
                    pnode->PushInventory(inv);
                });
                return true;
            }
        }
    }
    return false;
}
set<uint256> CWalletTx::GetConflicts() const