Fix amount calculation in supplier invoices with moves browsed multiple times

get_amount function must process invoices only one time (despite passed more
than one time) because supplier invoices total_amount is multiplied by -1 when
it has accounting moves and if multiplied 2 (or any pair number) times it
returns the amount in the wrong sign.

issue3711
review3791002

invoice.py

@@ -568,13 +568,13 @@ class Invoice(Workflow, ModelSQL, ModelView):
                 tax_amount[invoice.id] = invoice.currency.round(
                     tax_amount[invoice.id])
 
-        invoices_move = []
-        invoices_no_move = []
+        invoices_move = set()
+        invoices_no_move = set()
         for invoice in invoices:
             if invoice.move:
-                invoices_move.append(invoice.id)
+                invoices_move.add(invoice.id)
             else:
-                invoices_no_move.append(invoice.id)
+                invoices_no_move.add(invoice.id)
         invoices_move = cls.browse(invoices_move)
         invoices_no_move = cls.browse(invoices_no_move)