The argument specified the json data to save to disk when registering
a new image into the image graph. If it is nil, then the given image
is serialized to json and that is written by default. This default
behavior is sufficient if the given image was originally deserialzed
from this jsonData to begin with which has always been the case.
Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)
Upstream-commit: 26184de8ab1dfe812094c55c9becd8ebb60ed7be
Component: engine
ade837e2a4