Use INSIGHTS_DATABASE variables in edxlocal role

The INSIGHTS_MYSQL_USER variable is not defined, so the Insights database user was not being created.

playbooks/roles/edxlocal/defaults/main.yml

@@ -23,8 +23,8 @@ edxlocal_database_users:
     }
   - {
       db: "{{ INSIGHTS_DATABASE_NAME | default(None) }}",
-      user: "{{ INSIGHTS_MYSQL_USER | default(None) }}",
-      pass: "{{ INSIGHTS_MYSQL_USER | default(None) }}"
+      user: "{{ INSIGHTS_DATABASE_USER | default(None) }}",
+      pass: "{{ INSIGHTS_DATABASE_PASSWORD | default(None) }}"
     }
   - {
       db: "{{ XQUEUE_MYSQL_DB_NAME | default(None) }}",