Stanford-oriented Datadog updates

* Datadog explicitly sets hostname in style Stanford uses (relies on
  /etc/hostname being accurate, requires reboot)
* Enables nginx status check module integration for datadog
* Installs nginx access log processor that counts HTTP response codes
  and emits events for the individual components
* Supporting updates to Stanford playbooks
* Updates to lots of other places to make sure that their logs appear
  where we expect