kubeadm upgrade checks the migration path for the existing CoreDNS
deployment pre-flight. Migration paths are defined for CoreDNS
versions, which are derived from the image tag used in the existing
deployment.
The kubeadm ClusterConfiguration.DNS.ImageMeta supports suffixing the
tag with a digest, but at upgrade time does not derive the version
correctly from an image with digest suffix, because DeployedDNSAddon
does not deal with digests correctly. This commit makes DeployedDNSAddon
digest-aware.
Signed-off-by: Markus Rudy <mr@edgeless.systems>
065066d1ab