Should killed process deref a jail?

[Kyle Evans]

Hi,

In doing some testing of qemu-user-static recently, I noticed that
killing the last process in a non-persist jail doesn't kill off the
jail:

root at viper:/usr/src# jail -c path=/ command=yes
## ^C out

root at viper:/usr/src# jls
   JID  IP Address      Hostname                      Path
   181                                                /

root at viper:/usr/src# ps fxJ 181
PID TT  STAT TIME COMMAND

As a result, I ended up with 82 jails pointed at my armv7 sysroot and
much surprise when I checked out `jls`. This vaguely smells like a
bug, is this something that should be fixed?

Thanks,

Kyle Evans