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.
{
    AssertLockHeld(cs_wallet); 
    
    
    
    bool needsDB = !pwalletdbEncryption;
    if (needsDB) {
        pwalletdbEncryption = &walletdb;
    }
    if (!CCryptoKeyStore::AddKeyPubKey(secret, pubkey)) {
        if (needsDB) pwalletdbEncryption = nullptr;
        return false;
    }
    if (needsDB) pwalletdbEncryption = nullptr;
    
    CScript script;
    script = GetScriptForDestination(pubkey.GetID());
    if (HaveWatchOnly(script)) {
        RemoveWatchOnly(script);
    }
    script = GetScriptForRawPubKey(pubkey);
    if (HaveWatchOnly(script)) {
        RemoveWatchOnly(script);
    }