title: worker not recovered - Current config state offset 5 is behind group assignment 20, reading to end of config log
body: <p>I am using a 3 nodes kafka connect cluster to write data from a source to to kafka topic and from topic to destination. Everything works fine in distributed mode but when one of the worker is stopped and then restarted then I am getting the below message. </p>
  
  <pre><code>[2017-09-13 23:48:44,519] WARN Catching up to assignment's config offset. (org.apache.kafka.connect.runtime.distributed.DistributedHerder:741)
  [2017-09-13 23:48:44,519] INFO Current config state offset 5 is behind group assignment 20, reading to end of config log (org.apache.kafka.connect.runtime.distributed.DistributedHerder:785)
  [2017-09-13 23:48:45,018] INFO Finished reading to end of log and updated config snapshot, new config log offset: 5 (org.apache.kafka.connect.runtime.distributed.DistributedHerder:789)
  [2017-09-13 23:48:45,018] INFO Current config state offset 5 does not match group assignment 20. Forcing rebalance. (org.apache.kafka.connect.runtime.distributed.DistributedHerder:765)
  [2017-09-13 23:48:45,018] INFO Rebalance started (org.apache.kafka.connect.runtime.distributed.DistributedHerder:1187)
  [2017-09-13 23:48:45,018] INFO Wasn't unable to resume work after last rebalance, can skip stopping connectors and tasks (org.apache.kafka.connect.runtime.distributed.DistributedHerder:1219)
  [2017-09-13 23:48:45,018] INFO (Re-)joining group connect-cluster (org.apache.kafka.clients.consumer.internals.AbstractCoordinator:432)
  [2017-09-13 23:48:45,023] INFO Successfully joined group connect-cluster with generation 38 (org.apache.kafka.clients.consumer.internals.AbstractCoordinator:399)
  [2017-09-13 23:48:45,023] INFO Joined group and got assignment: Assignment{error=0, leader='connect-1-e51c1e8b-c95a-406b-8c56-2a0d4fc432f6', leaderUrl='http://10.10.10.10:8083/', offset=20, connectorIds=[], taskIds=[oracle_jdbc_sink_test-0]} (org.apache.kafka.connect.runtime.distributed.DistributedHerder:1166)
  [2017-09-13 23:48:45,023] WARN Catching up to assignment's config offset. (org.apache.kafka.connect.runtime.distributed.DistributedHerder:741)
  [2017-09-13 23:48:45,023] INFO Current config state offset 5 is behind group assignment 20, reading to end of config log (org.apache.kafka.connect.runtime.distributed.DistributedHerder:785)
  [2017-09-13 23:48:45,535] INFO Finished reading to end of log and updated config snapshot, new config log offset: 5 (org.apache.kafka.connect.runtime.distributed.DistributedHerder:789)
  [2017-09-13 23:48:45,535] INFO Current config state offset 5 does not match group assignment 20. Forcing rebalance. (org.apache.kafka.connect.runtime.distributed.DistributedHerder:765)
  [2017-09-13 23:48:45,535] INFO Rebalance started (org.apache.kafka.connect.runtime.distributed.DistributedHerder:1187)
  [2017-09-13 23:48:45,535] INFO Wasn't unable to resume work after last rebalance, can skip stopping connectors and tasks (org.apache.kafka.connect.runtime.distributed.DistributedHerder:1219)
  [2017-09-13 23:48:45,535] INFO (Re-)joining group connect-cluster (org.apache.kafka.clients.consumer.internals.AbstractCoordinator:432)
  [2017-09-13 23:48:45,540] INFO Successfully joined group connect-cluster with generation 38 (org.apache.kafka.clients.consumer.internals.AbstractCoordinator:399)
  [2017-09-13 23:48:45,540] INFO Joined group and got assignment: Assignment{error=0, leader='connect-1-e51c1e8b-c95a-406b-8c56-2a0d4fc432f6', leaderUrl='http://10.10.10.10:8083/', offset=20, connectorIds=[], taskIds=[oracle_jdbc_sink_test-0]} (org.apache.kafka.connect.runtime.distributed.DistributedHerder:1166)
  [2017-09-13 23:48:45,540] WARN Catching up to assignment's config offset. (org.apache.kafka.connect.runtime.distributed.DistributedHerder:741)
  [2017-09-13 23:48:45,540] INFO Current config state offset 5 is behind group assignment 20, reading to end of config log (org.apache.kafka.connect.runtime.distributed.DistributedHerder:785)
  [2017-09-13 23:48:46,042] INFO Finished reading to end of log and updated config snapshot, new config log offset: 5 (org.apache.kafka.connect.runtime.distributed.DistributedHerder:789)
  [2017-09-13 23:48:46,042] INFO Current config state offset 5 does not match group assignment 20. Forcing rebalance. (org.apache.kafka.connect.runtime.distributed.DistributedHerder:765)
  [2017-09-13 23:48:46,042] INFO Rebalance started (org.apache.kafka.connect.runtime.distributed.DistributedHerder:1187)
  [2017-09-13 23:48:46,042] INFO Wasn't unable to resume work after last rebalance, can skip stopping connectors and tasks (org.apache.kafka.connect.runtime.distributed.DistributedHerder:1219)
  </code></pre>