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.
strError = strprintf("Error: This transaction requires a transaction fee of at least %s", FormatMoney(nFeeRequired));
        throw JSONRPCError(RPC_WALLET_ERROR, strError);
    }
    CValidationState state;
    if (!pwalletMain->CommitTransaction(wtxNew, reservekey, g_connman.get(), state)) {
        strError = strprintf("Error: The transaction was rejected! Reason given: %s", state.GetRejectReason());
        throw JSONRPCError(RPC_WALLET_ERROR, strError);
    }
}
UniValue sendtoaddress(const JSONRPCRequest& request)
{
    if (!EnsureWalletIsAvailable(request.fHelp))
        return NullUniValue;
    if (request.fHelp || request.params.size() < 2 || request.params.size() > 5)
        throw runtime_error(
            "sendtoaddress \"address\" amount ( \"comment\" \"comment_to\" subtractfeefromamount )\n"
            "\nSend an amount to a given address.\n"
            + HelpRequiringPassphrase() +
            "\nArguments:\n"
            "1. \"address\"            (string, required) The bitcoin address to send to.\n"
            "2. \"amount\"             (numeric or string, required) The amount in " + CURRENCY_UNIT + " to send. eg 0.1\n"
            "3. \"comment\"            (string, optional) A comment used to store what the transaction is for. \n"
            "                             This is not part of the transaction, just kept in your wallet.\n"
            "4. \"comment_to\"         (string, optional) A comment to store the name of the person or organization \n"
            "                             to which you're sending the transaction. This is not part of the \n"
            "                             transaction, just kept in your wallet.\n"
            "5. subtractfeefromamount  (boolean, optional, default=false) The fee will be deducted from the amount being sent.\n"
            "                             The recipient will receive less bitcoins than you enter in the amount field.\n"
            "\nResult:\n"
            "\"txid\"                  (string) The transaction id.\n"