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 (!pwalletdbEncryption->TxnBegin()) {
            delete pwalletdbEncryption;
            pwalletdbEncryption = nullptr;
            return false;
        }
        pwalletdbEncryption->WriteMasterKey(nMasterKeyMaxID, kMasterKey);
        if (!EncryptKeys(_vMasterKey))
        {
            pwalletdbEncryption->TxnAbort();
            delete pwalletdbEncryption;
            
            
            assert(false);
        }
        
        SetMinVersion(FEATURE_WALLETCRYPT, pwalletdbEncryption, true);
        if (!pwalletdbEncryption->TxnCommit()) {
            delete pwalletdbEncryption;
            
            
            assert(false);
        }
        delete pwalletdbEncryption;
        pwalletdbEncryption = nullptr;
        Lock();
        Unlock(strWalletPassphrase);
        
        if (IsHDEnabled()) {
            if (!SetHDMasterKey(GenerateNewHDMasterKey())) {
                return false;