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.
mutable CAmount nWatchCreditCached;
    mutable CAmount nImmatureWatchCreditCached;
    mutable CAmount nAvailableWatchCreditCached;
    mutable CAmount nChangeCached;
    CWalletTx()
    {
        Init(NULL);
    }
    CWalletTx(const CWallet* pwalletIn, CTransactionRef arg) : CMerkleTx(std::move(arg))
    {
        Init(pwalletIn);
    }
    void Init(const CWallet* pwalletIn)
    {
        pwallet = pwalletIn;
        mapValue.clear();
        vOrderForm.clear();
        fTimeReceivedIsTxTime = false;
        nTimeReceived = 0;
        nTimeSmart = 0;
        fFromMe = false;
        strFromAccount.clear();
        fDebitCached = false;
        fCreditCached = false;
        fImmatureCreditCached = false;
        fAvailableCreditCached = false;
        fWatchDebitCached = false;
        fWatchCreditCached = false;
        fImmatureWatchCreditCached = false;
        fAvailableWatchCreditCached = false;