Block direct access to ESDs

The `PHP` setting is the [default](https://github.com/shopware/shopware/blob/0449093fb28bfb7c65909c136e5a6af2f2cf8c64/_sql/migrations/231-update-redirectDownload-config-var.php#L16) anyways, so restricting direct access should not be a problem.
I would opt for using the default location for esd files: 
`location ^~ /files/552211cce724117c3178e3d22bec532ec/ {`

This may not be the best choice shopware made for the default esd location but it's the default now. And this config should work out of the box for most users so setting the path to the default seems like a sane choice.