Linsiyuan9

*More detailed description of your change, if necessary. The PR title and PR message become the squashed commit message, so use a separate comment to ping reviewers.* *Summary of testing...

KAFKA-18061 AddRaftVoter responds with error message "NONE" instead of null

7

*Fix building 'Response.errorMessage' with 'RaftUtil #addVoterResponse' and' RaftUtil#removeVoterResponse' for 'Errors.NONE' is not 'null' but 'NONE' because When 'errorMessage' is passed in as 'null', 'Errors#message' is used to generate a default...