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 (strOldWalletPass.length() < 1 || strNewWalletPass.length() < 1)
        throw runtime_error(
            "walletpassphrasechange <oldpassphrase> <newpassphrase>\n"
            "Changes the wallet passphrase from <oldpassphrase> to <newpassphrase>.");
    if (!pwalletMain->ChangeWalletPassphrase(strOldWalletPass, strNewWalletPass))
        throw JSONRPCError(RPC_WALLET_PASSPHRASE_INCORRECT, "Error: The wallet passphrase entered was incorrect.");
    return NullUniValue;
}
UniValue walletlock(const JSONRPCRequest& request)
{
    if (!EnsureWalletIsAvailable(request.fHelp))
        return NullUniValue;
    if (pwalletMain->IsCrypted() && (request.fHelp || request.params.size() != 0))
        throw runtime_error(
            "walletlock\n"
            "\nRemoves the wallet encryption key from memory, locking the wallet.\n"
            "After calling this method, you will need to call walletpassphrase again\n"
            "before being able to call any methods which require the wallet to be unlocked.\n"
            "\nExamples:\n"
            "\nSet the passphrase for 2 minutes to perform a transaction\n"
            + HelpExampleCli("walletpassphrase", "\"my pass phrase\" 120") +
            "\nPerform a send (requires passphrase set)\n"
            + HelpExampleCli("sendtoaddress", "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\" 1.0") +
            "\nClear the passphrase since we are done before 2 minutes is up\n"
            + HelpExampleCli("walletlock", "") +
            "\nAs json rpc call\n"
            + HelpExampleRpc("walletlock", "")
        );
    LOCK2(cs_main, pwalletMain->cs_wallet);
    if (request.fHelp)