Built against `master` branch 801dd40666d1e6009920ad3ff755c7bb993b2a62:

If I have no wallet.dat file and run:

    bitcoind -usehd=0

A new wallet.dat file is created and an HD seed is assigned.

I see an error message in the source:

    "Error loading %s: You can't disable HD on an already existing HD wallet or create new non-HD wallets."

but that doesn't get shown because `fFirstRun` is true, and so the code which checks for `-usehd` values doesn't run.

If it's no longer possible to create non-HD wallets, specifying -usehd=0 when creating a wallet should be an error, and not get silently ignored.
if (ser_action.ForRead())
            Init(nullptr);
        char fSpent = false;
        if (!ser_action.ForRead())
        {
            mapValue["fromaccount"] = strFromAccount;
            WriteOrderPos(nOrderPos, mapValue);
            if (nTimeSmart)
                mapValue["timesmart"] = strprintf("%u", nTimeSmart);
        }
        READWRITE(*(CMerkleTx*)this);
        std::vector<CMerkleTx> vUnused; 
        READWRITE(vUnused);
        READWRITE(mapValue);
        READWRITE(vOrderForm);
        READWRITE(fTimeReceivedIsTxTime);
        READWRITE(nTimeReceived);
        READWRITE(fFromMe);
        READWRITE(fSpent);
        if (ser_action.ForRead())
        {
            strFromAccount = mapValue["fromaccount"];
            ReadOrderPos(nOrderPos, mapValue);
            nTimeSmart = mapValue.count("timesmart") ? (unsigned int)atoi64(mapValue["timesmart"]) : 0;
        }
        mapValue.erase("fromaccount");
        mapValue.erase("spent");
        mapValue.erase("n");
        mapValue.erase("timesmart");