Clusters are kept separate using the shred-versions obtained from
contact-infos. However, this mechanism breaks if there are 2 instances
of the same identity key running on different clusters, because then one
of the two contact-infos have the right shred-version.
If a node has the contact-info with the matching shred-version, then it
will pass all associated crds values even if they belong to the other
instance. So the shred-version check breaks.
As a result we cannot support 2 instances of the same identity key
running on different clusters. To prevent that, this commit is exempting
node-instances from shred-version check so that they are always
propagated across clusters and halt one of the running duplicate
instances.
140abec6ef