eio: unify deletion of eina_file_ls's iterator.

Due to a bug with eio_file_stat_ls(), a previous patch
(73a23401ef) was written.

This patch change the way we delete returned eina iterator
from eina_file_ls in _eio_file_eina_ls_heavy() from a separate
thread, into eio_async_end() from the main thread.

To clarify the code, and avoid a useless call to
eina_iterator_free(), this patch also moves the deletion
of the same eina iterator from _eio_file_heavy() into
eio_async_end() as well.

src/lib/eio/eio_file.c

@@ -92,9 +92,7 @@ _eio_file_heavy(void *data, Ecore_Thread *thread)
 
    if (pack) ecore_thread_feedback(thread, pack);
 
-   eio_file_container_set(&async->ls.common, NULL);
-
-   eina_iterator_free(ls);
+   async->ls.ls = ls;
 }
 
 static void