Use cases:

• I as the owner of the VM would like to know the image properties used by
  nova when scheduling and building my VM even after the image is changed or
  deleted in glance.

• Especially I as the owner of an existing VM want to see the
  hw_vtpm_secret_security in the embedded image properties so that I can
  observe the default vTPM security mode applied to of my VM before I consent
  to such security change. See vTPM live migration.

• I as the owner of the VM want to detect if the admin needed to change
  any image properties in my behalf via nova-mange image_property set.

Upstream bp: https://bugs.launchpad.net/nova/+spec/image-properties-in-server-show