[#64889148] Add new server_names for Nagios
[#64889148] Add new server_names for Nagios

Since we no longer use Nagios, it seems that the time is right to look to rename the server_name in Nginx. For the purposes of backward-compatibility, and to ensure product agnosticism, I have added entries for:
- nagios
- nagios.*
- icinga
- icinga.*
- alert
- alert.*
- alerts
- alerts.*

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