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.

{
protected:
    CWallet* pwallet;
    int64_t nIndex;
    CPubKey vchPubKey;
public:
    CReserveKey(CWallet* pwalletIn)
    {
        nIndex = -1;
        pwallet = pwalletIn;
    }
    ~CReserveKey()
    {
        ReturnKey();
    }
    void ReturnKey();
    bool GetReservedKey(CPubKey &pubkey);
    void KeepKey();
    void KeepScript() { KeepKey(); }
};
/** 
 * Account information.
 * Stored in wallet with key "acc"+string account name.
 */
class CAccount