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 (changePosition != -1 && (changePosition < 0 || (unsigned int)changePosition > tx.vout.size()))
        throw JSONRPCError(RPC_INVALID_PARAMETER, "changePosition out of bounds");
    for (unsigned int idx = 0; idx < subtractFeeFromOutputs.size(); idx++) {
        int pos = subtractFeeFromOutputs[idx].get_int();
        if (setSubtractFeeFromOutputs.count(pos))
            throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid parameter, duplicated position: %d", pos));
        if (pos < 0)
            throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid parameter, negative position: %d", pos));
        if (pos >= int(tx.vout.size()))
            throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid parameter, position too large: %d", pos));
        setSubtractFeeFromOutputs.insert(pos);
    }
    CAmount nFeeOut;
    string strFailReason;
    if(!pwalletMain->FundTransaction(tx, nFeeOut, overrideEstimatedFeerate, feeRate, changePosition, strFailReason, includeWatching, lockUnspents, setSubtractFeeFromOutputs, reserveChangeKey, changeAddress))
        throw JSONRPCError(RPC_INTERNAL_ERROR, strFailReason);
    UniValue result(UniValue::VOBJ);
    result.push_back(Pair("hex", EncodeHexTx(tx)));
    result.push_back(Pair("changepos", changePosition));
    result.push_back(Pair("fee", ValueFromAmount(nFeeOut)));
    return result;
}
extern UniValue dumpprivkey(const JSONRPCRequest& request); 
extern UniValue importprivkey(const JSONRPCRequest& request);
extern UniValue importaddress(const JSONRPCRequest& request);
extern UniValue importpubkey(const JSONRPCRequest& request);
extern UniValue dumpwallet(const JSONRPCRequest& request);
extern UniValue importwallet(const JSONRPCRequest& request);
extern UniValue importprunedfunds(const JSONRPCRequest& request);
extern UniValue removeprunedfunds(const JSONRPCRequest& request);