kafka: Do not require key when sending a message (#17962)

Keys are helpful to ensure the strict ordering of messages, however currently the
code uses a random request id for every log, hence using the request-id
as a Kafka key is not serve any purpose;

This commit removes the usage of the key, to also fix the audit issue from
internal subsystem that does not have a request ID.

cmd/os-rename_nolinux.go

@@ -22,7 +22,7 @@ package cmd
 
 import "errors"
 
-// Rename captures time taken to call os.Rename
+// Rename2 is not implemented in a non linux environment
 func Rename2(src, dst string) (err error) {
 	defer updateOSMetrics(osMetricRename2, src, dst)(errors.New("not implemented, skipping"))
 	return errSkipFile