ConsumeMarkersActor is blocked when kafka becomes suddenly down

[JakubDziworski]

In my tests I stumbled upon a case where actor system wouldn't shutdown. Turned out that ConsumeMarkersActor was blocked by polling from kafka (https://stackoverflow.com/questions/50268622/kafka-consumer-hangs-on-poll-when-kafka-is-down). It happens if you shut down kafka before shutting down actor.

Reactive kafka already solved this issue (https://github.com/akka/alpakka-kafka/blob/master/core/src/main/resources/reference.conf#L57) so It would be good idea to use it.