VNET teardown changes (part I)

[Bjoern A. Zeeb]

Hi,

sorry for the cross-post;  Reply-To set.

I extracted a patch from projects VNET which tries to get the VNET teardown
more robust (and in a next step plug the remaining [TCP] memory leaks).

If anyone has an interest in testing some parts on a non-production setup
(you have been warned) please do so and report back to me (privately) in case
of success or panics.

There is more to come.

https://people.freebsd.org/~bz/20160222-01-projects-vnets.diff

Thanks,
Bjoern