New nodes joining (big) clusters cause more traffic in ping responses than needed

[thanodnl]

New nodes joining an existing cluster add the complete membership list to the list of updates in its own Dissemination. These updates should already being propagated within the cluster and thus not needed in the dissemination of this node.

Since ringpop currently transfers the complete changes list on ping responses the network traffic created because of this increases with the number of nodes. This violates the claim made in section 2 of the SWIM paper where they claim the message size does not increase with the number of nodes in the cluster.

Suggested solution is to not use the membership list a new node receives upon joining as updates in the Dissemination protocol.