(Maybe only when running 16.04 containers under 14.04?)

Also install instructor ssh keys (although lxc exec is also usable)

This works around a problem where sometimes 16.04 containers on
14.04 get wedged (even when running linux-image-generic-lts-xenial)

This is to remain consistent with the existing DNS and handouts
(not enough time to change everything right now!)

Build all of pc1-36

This allows the same ansible setup to run directly on the Mac Mini and
also inside a VTP VM.

In future we can add routing and NAT to the VTP VM, and OSPF to announce
routes, so that it can work on a single external IP address; this will let
it run in cloud environments other than the Mac Mini workshop-kit.

Unfortunately, one of the containers locked up during restart
which looks like an issue with lxd.  (Ansible by default is talking
to 5 containers concurrently)

Also: make remove_dhcp optional

- roles for nagios
- build nagios-master from gold-master
- update hostname and postfix myhostname
- configure static IP address and /etc/hosts

Now the roles apply to the container itself, not to the host.
This simplifies the playbooks.

Also update dpkg check to work properly when python in state "un"