With the containerd image store, image inspect calculated Size from the
selected manifest's packed descriptors only. It therefore underreported
locally stored data and differed from image list, whose Size also
includes unpacked snapshot usage.
This difference came from the two paths using separate size
calculations. Commit a46ce37d25 added packed and unpacked accounting to
image list, and e7980275c0 later combined both values in image-list
Size. The corresponding inspect calculation was not updated, and
cd11843df8 preserved its packed-only behavior when extracting
ImageInspect from GetImage.
Use the selected manifest summary total for inspect Size. The summary
already accounts for locally present content and unpacked snapshot usage
for the selected platform, so image inspect now uses the same accounting
basis as image list.
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>