use xqueue application user for migrations when

COMMON_MYSQL_MIGRATE_PASS is not set

playbooks/roles/xqueue/tasks/deploy.yml

@@ -65,9 +65,6 @@
   shell: >
     SERVICE_VARIANT=xqueue {{ xqueue_venv_bin }}/django-admin.py syncdb --migrate --noinput --settings=xqueue.aws_settings --pythonpath={{ xqueue_code_dir }}
   sudo_user: "{{ xqueue_user }}"
-  environment:
-    DB_MIGRATION_USER: "{{ COMMON_MYSQL_MIGRATE_USER }}"
-    DB_MIGRATION_PASS: "{{ COMMON_MYSQL_MIGRATE_PASS }}"
   when: migrate_db is defined and migrate_db|lower == "yes" and not COMMON_MYSQL_MIGRATE_PASS
   notify:
     - restart xqueue