Don't use IN clause to filter invoices

In this case, filtering using an IN clause may cost more than just looping over
all invoices as the IN clause could be very large.

review940002

invoice.py

@@ -606,14 +606,11 @@ class Invoice(Workflow, ModelSQL, ModelView):
         Currency = pool.get('currency.currency')
         Date = pool.get('ir.date')
 
-        computes = cls.search([
-                ('id', 'in', [i.id for i in invoices]),
-                ('state', '=', 'posted'),
-                ])
-
         today = Date.today()
         res = dict((x.id, _ZERO) for x in invoices)
-        for invoice in computes:
+        for invoice in invoices:
+            if invoice.state != 'posted':
+                continue
             amount = _ZERO
             amount_currency = _ZERO
             for line in invoice.lines_to_pay: