Having a half install is pretty useless, and if the students want
practice at installation, they should start at the beginning anyway.

It seems acceptable to install nfsen with no sources. You get no
nfsend process, but you do after adding a new source.

TODO:
- allow a list of netflow sources to be provided and inserted into config
  (for noc); if empty, provide a commented-out sample
- decide whether we want to fully install nfsen or only partially
  in the lab

Also parameterise snmp_allow_subnets for snmpd.conf

FIXME:
- make the snmp contact and location configurable
- make the list of ACL subnets configurable
- add the snmp v3 user
- add the snmp client configuration

We can't use this with dumb http mirror, but we could use it when
cloning over ssh

These are all the base setup steps, but leave the students
to complete the post-installation via the web interface

(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)