[VOTE] KIP-815: Replace KafkaConsumer with AdminClient in GetOffsetShell

[deng ziming]

  Hey all, I'm starting the voting on KIP-734.

 This supports a new OffsetSpec in GetOffsetShell so that we can easily 
determine the offset and timestamp of the message with the largest timestamp on 
a partition. This seems a simple change but replaced KafkaConsumer with 
AdminClient in GetOffsetShell.

Thanks,
Ziming Deng