MqttSessionSpec: MQTT server connector should re-connect given connect, subscribe, connect again, publish

[raboof]

java.lang.AssertionError: assertion failed: expected no StreamSupervisor children, but got [Actor[pekko://mqtt-spec/system/Materializers/StreamSupervisor-4/flow-295-0-unnamed#-741345539], Actor[pekko://mqtt-spec/system/Materializers/StreamSupervisor-4/flow-296-0-ignoreSink#1738476296]]