STABLE: desired_avg_gossip leads to long intervals between reception of STABILITY messages in large clusters

The time computed for the sending of STABLE is desired_avg_gossip * cluster-size *2. While this is OK for small clusters, it may be too big for large clusters.
On the other hand, if every member simply multicasts a STABLE message every (say) 30 seconds on average, then the number of messages sent grows with increasing cluster size.
Investigate a way to set a lower and upper limit for the making and delivery of STABILITY messages, e.g. the goal is to receive 1 stability message every 60s.

Besides increased traffic, however, this requires everyone to have a TCP connection to everybody else in the cluster in case of a TCP transport.

A better solution might be to have only a dedicated member (the coord) periodically multicast a STABLE message. Everyone replies with a (unicast) STABLE message and when the coord has received STABLE replies from everyone, it multicasts a STABILITY message. This would only require a multicast from the coord to everyone, establishing TCP connections from the coord to everyone (usually already exists because of the VIEW-CHANGE multicast), but everyone would reuse the same TCP connection to send the reply.