bhyve: allow for automatic destruction on power-off

[kaktus]

Summary

Introduce -D flag that allows for the VM to be destroyed on guest initiated power-off by the bhyve(8) process itself.
This is quality of life change that allows for simpler deployments without the need for bhyvectl --destroy.

Requested by: swills

[grehan]

Nice change. Don't forget to update the man page.

[kaktus]

Update man page.

@grehan happy for a MFC in say 2 weeks after commit to head?

[grehan]

happy for a MFC in say 2 weeks after commit to head?

Yep, sounds good.

[0mp]

LGTM when it comes to the manual.

Also, maybe Relnotes: yes?

[swills]

This is a really great, thank you so much! Overall, this looks very good, only noticed one minor question.

usr.sbin/bhyve/bhyverun.c

807 ↗

(On Diff #73551)

Not sure 1 still makes sense in this case. It's not indicating a failure or issue of some kind, is it?

[kaktus]

As mentioned on irc, I believe we're bound by the already defined exit codes, as describes in section EXIT STATUS of bhyve(8).