Add firewall rule for NSCA
Add firewall rule for NSCA

I'd really appreciate a look-over from @samjsharpe or @nickstenning to
make sure what I'm doing is the right thing here.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet