using edxapp_mysql_user_migrate user to run migrations

playbooks/roles/edxapp/tasks/service_variant_config.yml

@@ -100,15 +100,15 @@
     {{ edxapp_venv_bin}}/python manage.py lms syncdb --migrate --noinput --settings=aws_migrate
   when: fake_migrations is not defined and migrate_db is defined and migrate_db|lower == "yes" and COMMON_MYSQL_MIGRATE_PASS
   environment:
-    DB_MIGRATION_USER: "{{ EDXAPP_MYSQL_USER_MIGRATE }}"
-    DB_MIGRATION_PASS: "{{ EDXAPP_MYSQL_PASSWORD_MIGRATE }}"
+    DB_MIGRATION_USER: "{{ COMMON_MYSQL_MIGRATE_USER }}"
+    DB_MIGRATION_PASS: "{{ COMMON_MYSQL_MIGRATE_PASS }}"
   sudo_user: "{{ edxapp_user }}"
   notify:
   - "restart edxapp"
   - "restart edxapp_workers"
 
 # Syncdb with migrate when the default migrate user is not set,
-# in this case use the application user to run migrations
+# in this case use the EDXAPP_MYSQL_USER_MIGRATE user to run migrations
 - name: syncdb and migrate
   shell: >
     chdir={{ edxapp_code_dir }}