rocksdb.rocksdb_parts failed in buildbot, result content mismatch

rocksdb.rocksdb_parts                    w4 [ fail ]

        Test ended at 2017-08-14 10:28:14

CURRENT_TEST: rocksdb.rocksdb_parts

--- /usr/share/mysql/mysql-test/plugin/rocksdb/rocksdb/r/rocksdb_parts.result	2017-08-14 07:33:50.000000000 -0400

+++ /dev/shm/var/4/log/rocksdb_parts.reject	2017-08-14 10:28:13.978237626 -0400

@@ -49,7 +49,7 @@

 set rocksdb_force_index_records_in_range= 12;

 explain select * from t1 force index(col1) where col1=10;

 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

-1	SIMPLE	t1	ref	col1	col1	5	const	24	

+1	SIMPLE	t1	ref	col1	col1	5	const	12	

 select * from t1 force index(col1) where col1=10;

 pk	col1	col2

 1	10	10

mysqltest: Result content mismatch