### 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
*
     * @param[in]  psbtx PartiallySignedTransaction to fill in
     * @param[out] complete indicates whether the PSBT is now complete
     * @param[in]  sighash_type the sighash type to use when signing (if PSBT does not specify)
     * @param[in]  sign whether to sign or not
     * @param[in]  bip32derivs whether to fill in bip32 derivation information if available
     * @param[out] n_signed the number of inputs signed by this wallet
     * @param[in] finalize whether to create the final scriptSig or scriptWitness if possible
     * return error
     */
    TransactionError FillPSBT(PartiallySignedTransaction& psbtx,
                  bool& complete,
                  int sighash_type = SIGHASH_DEFAULT,
                  bool sign = true,
                  bool bip32derivs = true,
                  size_t* n_signed = nullptr,
                  bool finalize = true) const;
    /**
     * Submit the transaction to the node's mempool and then relay to peers.
     * Should be called after CreateTransaction unless you want to abort
     * broadcasting the transaction.
     *
     * @param[in] tx The transaction to be broadcast.
     * @param[in] mapValue key-values to be set on the transaction.
     * @param[in] orderForm BIP 70 / BIP 21 order form details to be set on the transaction.
     */
    void CommitTransaction(CTransactionRef tx, mapValue_t mapValue, std::vector<std::pair<std::string, std::string>> orderForm);
    
    bool SubmitTxMemoryPoolAndRelay(CWalletTx& wtx, std::string& err_string, bool relay) const;
    bool DummySignTx(CMutableTransaction &txNew, const std::set<CTxOut> &txouts, const CCoinControl* coin_control = nullptr) const