Nest: Fix export of tmpattrs through pipes

In most cases of export there is no need to store back temporary
attributes to rte, as receivers (protocols) access eattr list anyway.
But pipe copies the original rte with old values, so we should store
tmpattrs also during export.

Thanks to Paul Donohue for the bugreport.

nest/rt-table.c

@@ -618,6 +618,9 @@ export_filter_(struct channel *c, rte *rt0, rte **rt_free, linpool *pool, int si
       goto reject;
     }
 
+  /* Needed for pipes */
+  rte_store_tmp_attrs(rt, pool, NULL);
+
  accept:
   if (rt != rt0)
     *rt_free = rt;