northd: Fix leak of lflow scratchpads.

Dynamic strings that backs 'match' and 'actions' are never destroyed
and leaked on every lflow re-build cycle.

 28,224 bytes in 126 blocks are definitely lost in loss record 494 of 498
    at 0x483BD19: realloc (vg_replace_malloc.c:834)
    by 0x4AEF14: xrealloc (util.c:149)
    by 0x465533: ds_reserve (dynamic-string.c:63)
    by 0x46587B: ds_put_format_valist (dynamic-string.c:161)
    by 0x465956: ds_put_format (dynamic-string.c:142)
    by 0x42187F: build_ipv6_input_flows_for_lrouter_port (ovn-northd.c:11188)
    by 0x42187F: build_lswitch_and_lrouter_iterate_by_op (ovn-northd.c:11279)
    by 0x42187F: build_lswitch_and_lrouter_flows.constprop.0 (ovn-northd.c:11316)
    by 0x422503: build_lflows (ovn-northd.c:11398)
    by 0x42478D: ovnnb_db_run (ovn-northd.c:12334)
    by 0x42478D: ovn_db_run (ovn-northd.c:12927)
    by 0x408E84: main (ovn-northd.c:13333)

Fixes: ddf9f1d ("ovn-northd: reorganize processing of lflows")
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: 0-day Robot <robot@bytheb.org>

northd/ovn-northd.c

@@ -11296,6 +11296,9 @@ build_lswitch_and_lrouter_flows(struct hmap *datapaths, struct hmap *ports,
     }
     free(svc_check_match);
 
+    ds_destroy(&lsi.match);
+    ds_destroy(&lsi.actions);
+
     /* Legacy lswitch build - to be migrated. */
     build_lswitch_flows(datapaths, ports, lflows, mcgroups,
                         igmp_groups, lbs);