slapos_accounting: Fixup constraint

  Usage of raise it don't lead to inconsistency
  Since we can merge aggregated Packing Lists, now we consider the sum() rather the invidual comparation.

master/bt5/slapos_accounting/SkinTemplateItem/portal_skins/slapos_accounting/SaleInvoiceTransaction_isTotalPriceMatchingSalePackingList.py

 invoice = context
 specialise = context.getPortalObject().portal_preferences.getPreferredAggregatedSaleTradeCondition()
 if invoice.getSpecialise() != specialise:
-  raise TypeError('Only invoice specialised by %s shall be checked' % specialise)
+  return False
 
 if len(invoice.getCausalityRelatedList(portal_type=['Cloud Contract', 'Subscription Request'])) > 0:
   # Nothing to compare
   return True
 
-
 delivery_list = invoice.getCausalityValueList(portal_type='Sale Packing List')
 amount = len(delivery_list)
-if amount != 1:
-  raise TypeError('Wrong amount %s of related packing lists' % amount)
-delivery = delivery_list[0]
+if amount < 1:
+  return False
+
+amount = sum([delivery.getTotalPrice(use='use/trade/sale') for delivery in delivery_list])
 
-return delivery.getTotalPrice(use='use/trade/sale') == context.getTotalPrice(use='use/trade/sale')
+return amount == context.getTotalPrice(use='use/trade/sale')