[FIX] product: cut date to keep format '%Y-%m-%d'

Ensures the date format is '%Y-%m-%d', since it is the format of
pricelist.version_id.date_start/date_end.

opw-640436

addons/product/pricelist.py

@@ -197,6 +197,7 @@ class product_pricelist(osv.osv):
     def _price_rule_get_multi(self, cr, uid, pricelist, products_by_qty_by_partner, context=None):
         context = context or {}
         date = context.get('date') or time.strftime('%Y-%m-%d')
+        date = date[0:10]
 
         products = map(lambda x: x[0], products_by_qty_by_partner)
         currency_obj = self.pool.get('res.currency')