Do not create a stratifier statsupdate thread in passthrough mode since the stats always read zero

src/stratifier.c

@@ -4531,6 +4531,7 @@ int stratifier(proc_instance_t *pi)
 		create_pthread(&pth_blockupdate, blockupdate, ckp);
 
 	mutex_init(&sdata->stats_lock);
+	if (!ckp->passthrough)
 		create_pthread(&pth_statsupdate, statsupdate, ckp);
 
 	mutex_init(&sdata->share_lock);