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.
"       {\n"
            "         \"txid\":\"id\",    (string) The transaction id\n"
            "         \"vout\": n         (numeric) The output number\n"
            "       }\n"
            "       ,...\n"
            "     ]\n"
            "\nResult:\n"
            "true|false    (boolean) Whether the command was successful or not\n"
            "\nExamples:\n"
            "\nList the unspent transactions\n"
            + HelpExampleCli("listunspent", "") +
            "\nLock an unspent transaction\n"
            + HelpExampleCli("lockunspent", "false \"[{\\\"txid\\\":\\\"a08e6907dbbd3d809776dbfc5d82e371b764ed838b5655e72f463568df1aadf0\\\",\\\"vout\\\":1}]\"") +
            "\nList the locked transactions\n"
            + HelpExampleCli("listlockunspent", "") +
            "\nUnlock the transaction again\n"
            + HelpExampleCli("lockunspent", "true \"[{\\\"txid\\\":\\\"a08e6907dbbd3d809776dbfc5d82e371b764ed838b5655e72f463568df1aadf0\\\",\\\"vout\\\":1}]\"") +
            "\nAs a json rpc call\n"
            + HelpExampleRpc("lockunspent", "false, \"[{\\\"txid\\\":\\\"a08e6907dbbd3d809776dbfc5d82e371b764ed838b5655e72f463568df1aadf0\\\",\\\"vout\\\":1}]\"")
        );
    LOCK2(cs_main, pwalletMain->cs_wallet);
    if (request.params.size() == 1)
        RPCTypeCheck(request.params, boost::assign::list_of(UniValue::VBOOL));
    else
        RPCTypeCheck(request.params, boost::assign::list_of(UniValue::VBOOL)(UniValue::VARR));
    bool fUnlock = request.params[0].get_bool();
    if (request.params.size() == 1) {
        if (fUnlock)
            pwalletMain->UnlockAllCoins();
        return true;