Use internal EC2 instance ID for datadog Host value

[bbangert]

By default the datadog Python agent is picking up the machines external hostname and using it as the host value. This causes a mismatch in the Host values in Datadog, that also doesn't match the logging infra Host (internal hostname).

This value can be retrieved on startup from http://169.254.169.254/latest/meta-data/instance-id

[bbangert]

While we're at it, we should log instance type as well, so we can make comparisons later if/when we need to change instance type. The meta-data service makes that available as ..../instance-type