Process sale also when processing purchase

If Purchase.process creates new stock moves, Sale.process must be called to
consider this new moves.

review858002
(transplanted from 5c867861be6e5e79aa0fec4e0dc9ad4afb243441)

purchase.py

@@ -85,6 +85,13 @@ class Purchase:
         super(Purchase, cls).confirm(purchases)
         cls._sale_supply_process(purchases)
 
+    @classmethod
+    def process(cls, purchases):
+        super(Purchase, cls).process(purchases)
+        # If not yet confirmed, it will be processed by confirm
+        if any(p.state == 'confirmed' for p in purchases):
+            cls._sale_supply_process(purchases)
+
     @classmethod
     @ModelView.button
     @Workflow.transition('cancel')