MB-10928: Correct the status check for rollback

- status to match PROTOCOL_BINARY_RESPONSE_ROLLBACK,
not ENGINE_ROLLBACK

Change-Id:I53f0d150b6d4b8267e5bb460d13f51076029b4ad
Reviewed-on: http://review.couchbase.org/36572
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: abhinav dangeti <abhinav@couchbase.com>