db: Fix as_rate calculation in get_metrics function

kwollect/db/kwollect_setup_db.py

@@ -387,7 +387,7 @@ if as_rate:
   "END / EXTRACT(epoch FROM timestamp - LAG(timestamp) OVER w) AS value, " \
   "labels " \
 "FROM cte " \
-"WINDOW w AS (PARTITION BY metric_id, device_id, labels) "\
+"WINDOW w AS (PARTITION BY metric_id, device_id, labels ORDER BY timestamp ASC) "\
 "ORDER BY timestamp ASC"
 
 plpy.info(req)