Clear stock moves in staging when validating amendment

Closes #12999
(grafted from abebfcfa0616585fcea20e17b9bafd6413011964)

--HG--
branch : 6.0

modules/purchase_amendment/purchase.py

@@ -153,7 +153,7 @@ class Amendment(Workflow, ModelSQL, ModelView):
     @classmethod
     def _stock_moves(cls, line):
         for move in line.moves:
-            if move.state == 'draft':
+            if move.state in {'staging', 'draft'}:
                 yield move
 
 

modules/sale_amendment/sale.py

@@ -169,7 +169,7 @@ class Amendment(Workflow, ModelSQL, ModelView):
     @classmethod
     def _stock_moves(cls, line):
         for move in line.moves:
-            if move.state == 'draft':
+            if move.state in {'staging', 'draft'}:
                 yield move