Enable New Relic monitoring of Grade Reports on Stage

CHANGELOG.md

 - Role: edxapp
+  - Added `EDXAPP_CELERY_HIGH_MEM_QUEUE_MONITOR` to configure whether monitoring is enabled for the high-mem queue.
+
+- Role: edxapp
   - Added `EDXAPP_EXTRA_MIDDLEWARE_CLASSES` for configuring additional middleware logic.
 
 - Role: discovery

playbooks/roles/edxapp/defaults/main.yml

@@ -511,6 +511,7 @@ EDXAPP_REGISTRATION_EXTRA_FIELDS:
   city: "hidden"
   country: "required"
 
+EDXAPP_CELERY_HIGH_MEM_QUEUE_MONITOR: False
 EDXAPP_CELERY_WORKERS:
   - queue: low
     service_variant: cms
@@ -539,7 +540,7 @@ EDXAPP_CELERY_WORKERS:
   - queue: high_mem
     service_variant: lms
     concurrency: 1
-    monitor: False
+    monitor: "{{ EDXAPP_CELERY_HIGH_MEM_QUEUE_MONITOR }}"
     max_tasks_per_child: 1
 EDXAPP_RECALCULATE_GRADES_ROUTING_KEY: 'edx.lms.core.default'
 EDXAPP_POLICY_CHANGE_GRADES_ROUTING_KEY: 'edx.lms.core.default'