Dead connection detection gives false positives when no streams are open

The server only sends NOOP requests after there has been a successful "open stream" request. However, the client erroneously expects NOOP requests even if no streams are open, leading to "Dead connection detected" messages and the connection being unnecessarily closed and reopened.

This surfaces in the Kafka connector, where a worker task might need to open streams from only one Couchbase node in a multi-node cluster. In the current implementation, the DCP client still needs to open connections to all nodes in the Couchbase cluster in order to do persistence polling, and to properly respond to cluster topology changes, even if no streams are open on those nodes.

The false positives have no known impact on correctness. However, needlessly closing connections is inefficient, and it's surprising to see these reconnection warnings in the log.