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.
{
    LOCK(cs_wallet); 
    if (nWalletVersion >= nVersion)
        return true;
    
    if (fExplicit && nVersion > nWalletMaxVersion)
            nVersion = FEATURE_LATEST;
    nWalletVersion = nVersion;
    if (nVersion > nWalletMaxVersion)
        nWalletMaxVersion = nVersion;
    {
        CWalletDB* pwalletdb = pwalletdbIn ? pwalletdbIn : new CWalletDB(*dbw);
        if (nWalletVersion > 40000)
            pwalletdb->WriteMinVersion(nWalletVersion);
        if (!pwalletdbIn)
            delete pwalletdb;
    }
    return true;
}
bool CWallet::SetMaxVersion(int nVersion)
{
    LOCK(cs_wallet); 
    
    if (nWalletVersion > nVersion)
        return false;
    nWalletMaxVersion = nVersion;
    return true;
}
std::set<uint256> CWallet::GetConflicts(const uint256& txid) const