Add conditionals for DD, splunk and new relic.

playbooks/edx-east/jenkins_admin.yml

@@ -3,10 +3,19 @@
   hosts: all
   sudo: True
   gather_facts: True
+  vars:
+    ENABLE_DATADOG: False
+    ENABLE_SPLUNKFORWARDER: False
+    ENABLE_NEWRELIC: False
   roles:
     - aws
     - edx_ansible
     - user
     - jenkins_admin
     - hotg
-  - newrelic
+    - role: datadog
+      when: ENABLE_DATADOG
+    - role: splunkforwarder
+      when: ENABLE_SPLUNKFORWARDER
+    - role: newrelic
+      when: ENABLE_NEWRELIC