If one calls `fundrawtransaction`, the change address will be retrieved from the keypool, though, this key/address will always be returned to the pool, leading to the problem that the next `getnewaddress()` call will restult in the same key/address.

Either we remove the auto-change-address (users would need to call `getrawchangeaddress` first [current best practice anyway]) or we add a call to keep/mark a specific key/address as change (after one have sent the funded raw transaction).

Reported by @NicolasDorier on IRC.
{
        nChange += GetChange(txout);
        if (!MoneyRange(nChange))
            throw std::runtime_error(std::string(__func__) + ": value out of range");
    }
    return nChange;
}
CPubKey CWallet::GenerateNewHDMasterKey()
{
    CKey key;
    key.MakeNewKey(true);
    int64_t nCreationTime = GetTime();
    CKeyMetadata metadata(nCreationTime);
    
    CPubKey pubkey = key.GetPubKey();
    assert(key.VerifyPubKey(pubkey));
    
    metadata.hdKeypath     = "m";
    metadata.hdMasterKeyID = pubkey.GetID();
    {
        LOCK(cs_wallet);
        
        mapKeyMetadata[pubkey.GetID()] = metadata;
        
        if (!AddKeyPubKey(key, pubkey))
            throw std::runtime_error(std::string(__func__) + ": AddKeyPubKey failed");
    }
    return pubkey;
}
bool CWallet::SetHDMasterKey(const CPubKey& pubkey)