Add mirror to list of icinga smokey checks
Add mirror to list of icinga smokey checks

Smokey is already running on the monitoring machine and processing the
mirror feature file. This will add the results of that check to the
Nagios display.

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