When re-deploying a stack without re-resolving the image digest,
the service's ContainerSpec was updated with the image-reference
as specified in the stack/compose file.
As a result, the image-digest that was resolved in a previous
deploy was overwritten, causing the service to be re-deployed.
This patch preserves the previously resolve image-digest
by copying it from the current service spec.
A unit test is also added to verify that the image information
in the service spec is not updated if QueryRegistry is disabled.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
d0bea64185