Add close stale connections and strict cluster member check flags to ClusterClientOptions

[mp911de]

Add two flags to ClusterClientOptions:

• closeStaleConnections: Close stale connections when refreshing the cluster topology
  Motivation: Connections to nodes, which do not belong to the cluster (anymore) are closed as soon as the cluster topology changes. If one node is no longer part of the cluster, the connections to the node can be closed. One might want to prevent that behavior because one might want still to communicate with the other nodes that come into play when using validateClusterNodeMembership = false
• validateClusterNodeMembership: Validate the cluster node membership before allowing connections to that node
  Motivation: The current implementation performs redirects using MOVED and ASK and allows obtaining connections to the particular cluster nodes. The validation was introduced during the development of version 3.3 to prevent security breaches and only allow connections to the known hosts of the CLUSTER NODES output. There are some scenarios, where the strict validation is an obstruction:
  • MOVED/ASK redirection but the cluster topology view is stale
  • Connecting to cluster nodes using different IP's/hostnames (e.g. private/public IP's)
  • Connecting to non-cluster members to reconfigure those while using the RedisClusterClient connection.

[mp911de]

Implemented.