### Describe the issue
Because transaction malleability isn't that much of an issue lately, we've decided to let the wallet spend zero conf change. It has happened that we create a transaction just moments before a significant increase in (higher paying) transactions. Because of #9645, there is a chance that you end up with an unconfirmed chain of 24 child transactions. If you let the wallet produce a 25th child, it will return an error because the mempool won't accept it.  This is also problematic in the case we would like to cpfp the whole chain, because other nodes won't relay the transaction to the miners.

### Can you reliably reproduce the issue?
#### If so, please list the steps to reproduce below:
1. Predict an increase in transactions. (You need a crystal ball)
2. Create transaction
3. Create more transactions
4. ?
5. Profit

### Expected behaviour
Ideally it would stop if the chain is 24 transactions long, so one could try a cpfp transaction to compensate for the fees.

### Actual behaviour
It will create a transaction chain of 25 transaction, making it hard to have the whole chain confirmed in a certain time.

### What version of bitcoin-core are you using?
Official binary: 0.13.1
* block locator and m_last_block_processed, and registering for
     * notifications about new blocks and transactions.
     */
    static bool AttachChain(const std::shared_ptr<CWallet>& wallet, interfaces::Chain& chain, const bool rescan_required, bilingual_str& error, std::vector<bilingual_str>& warnings);
public:
    /**
     * Main wallet lock.
     * This lock protects all the fields added by CWallet.
     */
    mutable RecursiveMutex cs_wallet;
    WalletDatabase& GetDatabase() const override
    {
        assert(static_cast<bool>(m_database));
        return *m_database;
    }
    /** Get a name for this wallet for logging/debugging purposes.
     */
    const std::string& GetName() const { return m_name; }
    typedef std::map<unsigned int, CMasterKey> MasterKeyMap;
    MasterKeyMap mapMasterKeys;
    unsigned int nMasterKeyMaxID = 0;
    
    CWallet(interfaces::Chain* chain, const std::string& name, const ArgsManager& args, std::unique_ptr<WalletDatabase> database)
        : m_args(args),
          m_chain(chain),
          m_name(name),
          m_database(std::move(database))
    {
    }
    ~CWallet()