[FIX] stock: add location in context on prodlot search

To be consistant with the results of _get_stock. Otherwise search made on
stock_available may not display results with the same value than the search
criteria.
Fixes #3976

addons/stock/stock.py

@@ -1437,7 +1437,15 @@ class stock_production_lot(osv.osv):
         """ Searches Ids of products
         @return: Ids of locations
         """
-        locations = self.pool.get('stock.location').search(cr, uid, [('usage', '=', 'internal')])
+        if context is None:
+            context = {}
+
+        if 'location_id' not in context:
+            locations = self.pool['stock.location'].search(
+                cr, uid, [('usage', '=', 'internal')], context=context)
+        else:
+            locations = context['location_id'] and [context['location_id']] or []
+
         cr.execute('''select
                 prodlot_id,
                 sum(qty)