Add a default garden.persistent_image_list
Add a default garden.persistent_image_list

[#103863836]

Signed-off-by: Jen Spinney <475b118f8db4f150e7ed3b69b35fd7c857f9c9f8@hp.com>

cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release