AUTO-413: Use an internal app for statsd preview

- We are running statsd exporter as an app with a public route for
  Prometheus to scrape
- This updates preview to send statsd metrics over the CF internal
  networking to the statsd exporter
- Removes the sidecar statsd exporters too

manifest.yml.j2

@@ -10,8 +10,8 @@
 
   'notify-delivery-celery-beat': {'memory': '128M'},
   'notify-delivery-worker-jobs': {},
-  'notify-delivery-worker-research': {'local_statsd': ['preview', 'staging']},
-  'notify-delivery-worker-sender': {'disk_quota': '2G', 'memory': '3G', 'local_statsd': ['preview', 'staging']},
+  'notify-delivery-worker-research': {},
+  'notify-delivery-worker-sender': {'disk_quota': '2G', 'memory': '3G'},
   'notify-delivery-worker-periodic': {},
   'notify-delivery-worker-priority': {},
   'notify-delivery-worker-letters': {},
@@ -49,9 +49,6 @@ applications:
     services:
       - notify-db
       - logit-ssl-syslog-drain
-      {% if environment in app.get('local_statsd', []) -%}
-      - notify-prometheus
-      {% endif %}
 
     env:
       NOTIFY_APP_NAME: {{ app.get('NOTIFY_APP_NAME', CF_APP.replace('notify-', '')) }}
@@ -77,8 +74,8 @@ applications:
       AWS_ACCESS_KEY_ID: '{{ AWS_ACCESS_KEY_ID }}'
       AWS_SECRET_ACCESS_KEY: '{{ AWS_SECRET_ACCESS_KEY }}'
 
-      {% if environment in app.get('local_statsd', []) %}
-      STATSD_HOST: "localhost"
+      {% if environment == 'preview' %}
+      STATSD_HOST: "notify-statsd-exporter-{{ environment }}.apps.internal"
       STATSD_PREFIX: ""
       {% else %}
       STATSD_HOST: "statsd.hostedgraphite.com"