Do not copy before carriages and after carriages

The carriages field is already copying the values.

issue11820
review418461003

sale.py

@@ -88,6 +88,16 @@ class Sale(metaclass=PoolMeta):
                 pattern['after_carrier'] = 'buyer'
         return pattern
 
+    @classmethod
+    def copy(cls, sales, default=None):
+        if default is None:
+            default = {}
+        else:
+            default = default.copy()
+        default.setdefault('before_carriages')
+        default.setdefault('after_carriages')
+        return super().copy(sales, default=default)
+
 
 class Line(metaclass=PoolMeta):
     __name__ = 'sale.line'

stock.py

@@ -126,6 +126,16 @@ class _ShipmentMixin:
         super().delete(shipments)
         Carriage.delete(carriages)
 
+    @classmethod
+    def copy(cls, shipments, default=None):
+        if default is None:
+            default = {}
+        else:
+            default = default.copy()
+        default.setdefault('before_carriages')
+        default.setdefault('after_carriages')
+        return super().copy(shipments, default=default)
+
 
 class Carriage_Sale(ShipmentCostSaleMixin, metaclass=PoolMeta):
     __name__ = 'stock.shipment.carriage'