Add status check for admin app

The /_status endpoint should return 200 if everything is OK and fail
otherwise.
Merge pull request #488 from alphagov/admin-status-check

Add status check for admin app
Allow use of both public and wildcard keys

In production we want to be able to include both the wildcard
(*..performance.service.gov.uk) and the public
(*.performance.service.gov.uk) keys and certs.

Needed to update hiera to be able to reference hiera vars in yaml
Revert logstash sensu handler

Sensu community plugins updated the logstash handler to use a message
only accepted by logstash 1.2, not 1.1 which we use. This is the
previous working version, which is vendored here rather than
forking sensu-community-plugins again.

See
https://github.com/sensu/sensu-community-plugins/commit/b2257d7e8a17696fb7d0f1451a7ce2fe5c14320f#diff-e6d2ad1f8e19a38c7f6e8c1e87d7961d
and
https://logstash.jira.com/browse/LOGSTASH-675
Merge pull request #489 from alphagov/public-and-env-ssl-keys

Allow use of both public and wildcard keys
Merge pull request #490 from alphagov/sensu-alerts-back-in-logstash

Revert logstash sensu handler
All jumpbox vhosts need the environment cert

All the vhosts on the jumbpox, for management services, use environment
specific domain names (*.<environment>.performance.service.gov.uk) and
never the public domain names (*.performance.service.gov.uk). This means
that we need to ensure they always have the environment cert.
Merge pull request #491 from alphagov/public-and-env-ssl-keys

All jumpbox vhosts need the environment cert