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.
{
        if (!coinControl.IsSelected(txin.prevout))
        {
            tx.vin.push_back(txin);
            if (lockUnspents)
            {
              LOCK2(cs_main, cs_wallet);
              LockCoin(txin.prevout);
            }
        }
    }
    
    if (keepReserveKey)
        reservekey.KeepKey();
    return true;
}
bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend, CWalletTx& wtxNew, CReserveKey& reservekey, CAmount& nFeeRet,