Fix a random result mismatch of encryption.innodb_encrypt_log

Disable change buffering, so that some data that was previously
written to the encrypted redo log will not end up being copied
to the unencrypted redo log due to change buffer merge.

mysql-test/suite/encryption/r/innodb_encrypt_log.result

@@ -25,6 +25,7 @@ CREATE TEMPORARY TABLE t LIKE t0;
 INSERT INTO t VALUES
 (NULL,1,1,'private','secret'),(NULL,2,2,'sacred','success'),
 (NULL,3,3,'story','secure'),(NULL,4,4,'security','sacrament');
+SET GLOBAL innodb_change_buffering=none;
 SET GLOBAL innodb_flush_log_at_trx_commit=1;
 INSERT INTO t0
 SELECT NULL, t1.col_int, t1.col_int_key, t1.col_char, t1.col_char_key