Due to prefix matching, worker-1's node_topic() also matched worker-10,
worker-11, etc. Suffix the node topic with a `.`. The original implementation
came from NATS, where subjects are separated by `.`.
Adapt nodeid_topic() for consistency.
When two workers connect to zeek.cluster.worker, the central ZeroMQ
proxy would not propagate unsubscription information to other nodes
once they both left. Set ZMQ_XPUB_VERBOSER on the proxies XPUB socket
for visibility.
This is a cluster backend implementation using a central XPUB/XSUB proxy
that by default runs on the manager node. Logging is implemented leveraging
PUSH/PULL sockets between logger and other nodes, rather than going
through XPUB/XSUB.
The test-all-policy-cluster baseline changed: Previously, Broker::peer()
would be called from setup-connections.zeek, causing the IO loop to be
alive. With the ZeroMQ backend, the IO loop is only alive when
Cluster::init() is called, but that doesn't happen anymore.
