14.04 -> 16.04 upgrade in lxd container dies most of the way through

[Michael Hudson-Doyle]

This sounds a bit like bug #1555237 but I'm not sure it's the same.

Basically I did this: started a lxd container with "lxd launch ubuntu-daily:trusty", sshed into it (I have cloud-init data configured to set this up) and ran do-release-upgrade -d. I answered "no" to all questions (restart services without asking, asked it not to restart anything due to the openssl upgrade, not to replace whichever file you get asked about) and then, finally, as it was asking me if I wanted to reboot or not, my ssh session dropped (it had probably been idle at that prompt for a while).

I see this when I log back in:

ubuntu@lts2lts:~$ sudo screen -ls
sudo: unable to resolve host lts2lts
There is a screen on:
 2413.ubuntu-release-upgrade-screen-window (03/29/2016 02:37:27 AM) (Dead ???)
Remove dead screens with 'screen -wipe'.
1 Socket in /var/run/screen/S-root.

And while I haven't checked exactly, it seems like the container has "rebooted".

I've uploaded /var/log/dist-upgrade/ from the container to http://people.canonical.com/~mwh/dist-upgrade-logs.tgz.

This seems to be reproducible, although exactly when the ssh connection drops seems a bit variable.