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.
{
protected:
    CWallet* pwallet;
    int64_t nIndex;
    CPubKey vchPubKey;
    bool fInternal;
public:
    explicit CReserveKey(CWallet* pwalletIn)
    {
        nIndex = -1;
        pwallet = pwalletIn;
        fInternal = false;
    }
    CReserveKey() = default;
    CReserveKey(const CReserveKey&) = delete;
    CReserveKey& operator=(const CReserveKey&) = delete;
    ~CReserveKey()
    {
        ReturnKey();
    }
    void ReturnKey();
    bool GetReservedKey(CPubKey &pubkey, bool internal = false);
    void KeepKey();
    void KeepScript() override { KeepKey(); }
};
/** 
 * Account information.
 * Stored in wallet with key "acc"+string account name.
 */
class CAccount