WIP: demonstrate usage of vnet shutdown stage

[zlei]

Summary

Previous discussing about vnet shutdown stage: https://lists.freebsd.org/archives/freebsd-jail/2022-December/000173.html

1. Purge all route entries on vnet shutdown
2. Delete all interface IPv[46] addresses
3. Return all loaned interfaces to their parent vnets on vnet shutdown, prior to vnet destroying

[zlei]

sys/netinet6/ip6_input.c

352

TODO: LOR panic here

[zlei]

This comment was removed by zlei.