This happening on every group-delete. In side effect of this the subnet 'a4619bfb-aa80-4850-af02-54f47a7b1b8e' for which the error message is coming, doesn't get deleted any time.
2015-10-27 16:12:10.060 6825 INFO neutron.plugins.ml2.plugin [-] Subnet a4619bfb-aa80-4850-af02-54f47a7b1b8e was deleted concurrently
This happening on every group-delete. In side effect of this the subnet 'a4619bfb- aa80-4850- af02-54f47a7b1b 8e' for which the error message is coming, doesn't get deleted any time.
2015-10-27 16:12:10.060 6825 INFO neutron. plugins. ml2.plugin [-] Subnet a4619bfb- aa80-4850- af02-54f47a7b1b 8e was deleted concurrently