If one calls `fundrawtransaction`, the change address will be retrieved from the keypool, though, this key/address will always be returned to the pool, leading to the problem that the next `getnewaddress()` call will restult in the same key/address.

Either we remove the auto-change-address (users would need to call `getrawchangeaddress` first [current best practice anyway]) or we add a call to keep/mark a specific key/address as change (after one have sent the funded raw transaction).

Reported by @NicolasDorier on IRC.
* Insert additional inputs into the transaction by
     * calling CreateTransaction();
     */
    bool FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, bool overrideEstimatedFeeRate, const CFeeRate& specificFeeRate, int& nChangePosInOut, std::string& strFailReason, bool includeWatching, bool lockUnspents, const std::set<int>& setSubtractFeeFromOutputs, bool keepReserveKey = true, const CTxDestination& destChange = CNoDestination());
    /**
     * Create a new transaction paying the recipients with a set of coins
     * selected by SelectCoins(); Also create the change output, when needed
     * @note passing nChangePosInOut as -1 will result in setting a random position
     */
    bool CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletTx& wtxNew, CReserveKey& reservekey, CAmount& nFeeRet, int& nChangePosInOut,
                           std::string& strFailReason, const CCoinControl *coinControl = NULL, bool sign = true);
    bool CommitTransaction(CWalletTx& wtxNew, CReserveKey& reservekey, CConnman* connman, CValidationState& state);
    void ListAccountCreditDebit(const std::string& strAccount, std::list<CAccountingEntry>& entries);
    bool AddAccountingEntry(const CAccountingEntry&);
    bool AddAccountingEntry(const CAccountingEntry&, CWalletDB *pwalletdb);
    static CFeeRate minTxFee;
    static CFeeRate fallbackFee;
    /**
     * Estimate the minimum fee considering user set parameters
     * and the required fee
     */
    static CAmount GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarget, const CTxMemPool& pool);
    /**
     * Return the minimum required fee taking into account the
     * floating relay fee and user set minimum transaction fee
     */
    static CAmount GetRequiredFee(unsigned int nTxBytes);
    bool NewKeyPool();
    bool TopUpKeyPool(unsigned int kpSize = 0);
    void ReserveKeyFromKeyPool(int64_t& nIndex, CKeyPool& keypool);