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.
}
        else
            LogPrintf("Allowing wallet upgrade up to %i\n", nMaxVersion);
        if (nMaxVersion < walletInstance->GetVersion())
        {
            InitError(_("Cannot downgrade wallet"));
            return nullptr;
        }
        walletInstance->SetMaxVersion(nMaxVersion);
    }
    if (fFirstRun)
    {
        
        walletInstance->SetMinVersion(FEATURE_NO_DEFAULT_KEY);
        
        CPubKey masterPubKey = walletInstance->GenerateNewHDMasterKey();
        if (!walletInstance->SetHDMasterKey(masterPubKey))
            throw std::runtime_error(std::string(__func__) + ": Storing master key failed");
        
        if (!walletInstance->TopUpKeyPool()) {
            InitError(_("Unable to generate initial keys") += "\n");
            return NULL;
        }
        walletInstance->SetBestChain(chainActive.GetLocator());
    }
    else if (gArgs.IsArgSet("-usehd")) {
        bool useHD = gArgs.GetBoolArg("-usehd", DEFAULT_USE_HD_WALLET);
        if (walletInstance->IsHDEnabled() && !useHD) {
            InitError(strprintf(_("Error loading %s: You can't disable HD on an already existing HD wallet or create new non-HD wallets."), walletFile));
            return nullptr;