Enable NPN

Next Protocol Negotiation extension. See https://technotes.googlecode.com/git/nextprotoneg.html
This seems to be fixed now

I was getting an error about duplicate client_max_body_size directive.
Configure unattended upgrades appropriately

Take from GOV.UK puppet. Picked up the ITHC that we didn’t appear to be
installing things in the background that we could do.
Merge pull request #663 from alphagov/feature/npn

Enable NPN
Merge pull request #670 from alphagov/feature/unattended-upgrades

Configure unattended upgrades appropriately