If we mix two types of global discounts, then one of the line is recomputed
again and messes up all the numbers.

STEPS:

* configure global discount 10% and "discount on order" via coupons
* Open POS > Add Large Meeting Table $ 3600
* Apply coupon, then apply global discount

The problem happens because `baseToDiscount` already includes "discount on
order", which is later recomputed again at
https://github.com/odoo/odoo/blob/a3c236ef0e047127583f6565461f0b90781584e4/addons/pos_loyalty/static/src/js/Loyalty.js#L452-L455

BEFORE:

```
Large Meeting Table: $3600.00
[DISC] Discount (10%, No tax): -$324.00
10% on you order: -$327.60
```

AFTER:

```
Large Meeting Table: $3600.00
[DISC] Discount (10%, No tax): -$324.00
10% on you order: -$360
```

The problem is not reproduced in 16.2 since the following refactoring
https://github.com/odoo/odoo/commit/c7fbae7a343dd90f8449ed94530f1fa2e6070690



opw-3187406

closes odoo/odoo#113762

Signed-off-by: Ivan Elizaryev (iel) <iel@odoo.com>