KafkaFlow may lose an error if retry strategy fails

[rtar]

KafkaFlow may lose an error if retry strategy fails at the following line:
https://github.com/evolution-gaming/kafka-flow/blob/master/core/src/main/scala/com/evolutiongaming/kafka/flow/KafkaFlow.scala#L81

The problem is that as the join is never called the, if fiber dies with an error, the Resource will never be cancelled and the application will just happily hang.