[CASSANDRA-18999] Gossiper::hasMajorVersion3Nodes returns true when a cluster is upgrading patch version without Cassandra 3 nodes.
This commit fixes Gossiper::hasMajorVersion3Nodes so that it does not return true when all hosts have a known version, no hosts are on a version earlier than 4.0, and there is a 4.x minor version or patch version upgrade in progress. Additionally, this commit improves the clarity of Gossiper::hasMajorVersion3Nodes's name to indicate that it will return true when the cluster has 3.x nodes or if the cluster state is unknown, matching the description in the in-line comment.
patch by Isaac Reath; reviewed by Paulo Motta and Stefan Miklosovic for CASSANDRA-18999
Closes #2967
6 files changed
