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.
{
    LOCK(cs_nWalletUnlockTime);
    nWalletUnlockTime = 0;
    pWallet->Lock();
}
UniValue walletpassphrase(const JSONRPCRequest& request)
{
    if (!EnsureWalletIsAvailable(request.fHelp))
        return NullUniValue;
    if (pwalletMain->IsCrypted() && (request.fHelp || request.params.size() != 2))
        throw runtime_error(
            "walletpassphrase \"passphrase\" timeout\n"
            "\nStores the wallet decryption key in memory for 'timeout' seconds.\n"
            "This is needed prior to performing transactions related to private keys such as sending bitcoins\n"
            "\nArguments:\n"
            "1. \"passphrase\"     (string, required) The wallet passphrase\n"
            "2. timeout            (numeric, required) The time to keep the decryption key in seconds.\n"
            "\nNote:\n"
            "Issuing the walletpassphrase command while the wallet is already unlocked will set a new unlock\n"
            "time that overrides the old one.\n"
            "\nExamples:\n"
            "\nunlock the wallet for 60 seconds\n"
            + HelpExampleCli("walletpassphrase", "\"my pass phrase\" 60") +
            "\nLock the wallet again (before 60 seconds)\n"
            + HelpExampleCli("walletlock", "") +
            "\nAs json rpc call\n"