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.
return true;
    if (!pwalletMain->IsCrypted())
        throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE, "Error: running with an unencrypted wallet, but walletlock was called.");
    {
        LOCK(cs_nWalletUnlockTime);
        pwalletMain->Lock();
        nWalletUnlockTime = 0;
    }
    return NullUniValue;
}
UniValue encryptwallet(const JSONRPCRequest& request)
{
    if (!EnsureWalletIsAvailable(request.fHelp))
        return NullUniValue;
    if (!pwalletMain->IsCrypted() && (request.fHelp || request.params.size() != 1))
        throw runtime_error(
            "encryptwallet \"passphrase\"\n"
            "\nEncrypts the wallet with 'passphrase'. This is for first time encryption.\n"
            "After this, any calls that interact with private keys such as sending or signing \n"
            "will require the passphrase to be set prior the making these calls.\n"
            "Use the walletpassphrase call for this, and then walletlock call.\n"
            "If the wallet is already encrypted, use the walletpassphrasechange call.\n"
            "Note that this will shutdown the server.\n"
            "\nArguments:\n"
            "1. \"passphrase\"    (string) The pass phrase to encrypt the wallet with. It must be at least 1 character, but should be long.\n"
            "\nExamples:\n"
            "\nEncrypt you wallet\n"
            + HelpExampleCli("encryptwallet", "\"my pass phrase\"") +
            "\nNow set the passphrase to use the wallet, such as for signing or sending bitcoin\n"
            + HelpExampleCli("walletpassphrase", "\"my pass phrase\"") +