EFS should be independent of lifecycle of elasticbean environment

The [tutorial for Deploying a High-Availability WordPress Website](https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/php-hawordpress-tutorial.html) talks about creating an RDS instance external to the elasticbean. The tutorial uses an EFS that is created using [efs-mount in .ebextensions](https://github.com/awslabs/eb-php-wordpress/blob/8e5a386b56923443fd35ad9824db87f99faace64/.ebextensions/efs-create.config#L1) and is symlinked to ``wp-content/uploads``. The ``uploads`` directory in wordpress is used to store the media files.

Since this EFS volume is created through elasticbean, what this means is that if the EB is terminated, the files stored on ``uploads`` are deleted as well. The intent is that the ``uploads`` directory has non-ephemeral files that need to shared across all the instances. Deleting the files when the instance terminates is counter to this intent.

To be consistent, I think both the EFS and RDS should be created outside the elasticbean environment.

AWS High-Availability WordPress tutorial と .ebextensions/efs-create.config から始め、次に EFS ボリュームがどのように作成され、wp-content/uploads にリンクされるかを追跡します。そのライフサイクルを、外部で作成された RDS インスタンスのライフサイクルと比較します。uploads EFS が Elastic Beanstalk 環境の外部にあり、環境が終了しても存続すれば完了です。

索引モデルが issue の本文から書いたものです。