sandbox-ora: Allow to deactivate creation of the xqueue DB

The mysql_db command from ansible expects to be able to connect to the
`mysql` DB, which prevents changing the MySQL DB for xqueue to a
DB on which we don't have overall administrator privileges.

https://github.com/ansible/ansible/blob/devel/library/database/mysql_db

playbooks/roles/xqueue/tasks/main.yml

@@ -25,6 +25,7 @@
     login_password={{xqueue_auth_config.DATABASES.default.PASSWORD}}
     state=present
     encoding=utf8
+  when: xqueue_create_db is defined and xqueue_create_db|lower == "yes"
 
 - name: xqueue | create xqueue application config
   template: src=xqueue.env.json.j2 dest={{app_base_dir}}/xqueue.env.json mode=0640 owner={{ xqueue_user }} group=adm

playbooks/roles/xqueue/vars/main.yml

@@ -39,6 +39,7 @@ xqueue_auth_config:
   'DATABASES':
     'default': { 'ENGINE': 'django.db.backends.mysql', 'NAME': 'xqueue', 'USER': 'root', 'PASSWORD': '', 'HOST': 'localhost', 'PORT': '3306' }
 
+xqueue_create_db: 'yes'
 xqueue_source_repo: https://github.com/edx/xqueue.git
 xqueue_version: 'HEAD'
 xqueue_pre_requirements_file:    "{{ xqueue_code_dir }}/pre-requirements.txt"