bob subscribes to namespace scenario33-pubsub-c6228a on node-2
  subscribe returned HTTP 201
settle 2s for subscription settle
  bob subscriptions: 1 entries; contains ns: True
alice writes M1 into the subscribed namespace
settle 6s for write fanout to subscribers
  bob sees M1 in subscribed namespace: 1
bob unsubscribes from scenario33-pubsub-c6228a
  unsubscribe returned HTTP 200
settle 2s for unsubscribe settle
  bob subscriptions after unsubscribe: ns still present = False
alice writes M2 post-unsubscribe (may still replicate via federation but subscription list excludes ns)
settle 5s for post-unsubscribe settle