rocksdb.2pc_group_commit fails intermittently in BB

rocksdb.2pc_group_commit 'write_prepared' w1 [ fail ]

        Test ended at 2018-09-11 13:12:58

CURRENT_TEST: rocksdb.2pc_group_commit

--- /mnt/buildbot/build/mariadb-10.2.18/storage/rocksdb/mysql-test/rocksdb/r/2pc_group_commit.result	2018-09-11 10:28:11.000000000 -0400

+++ /mnt/buildbot/build/mariadb-10.2.18/storage/rocksdb/mysql-test/rocksdb/r/2pc_group_commit.reject	2018-09-11 13:12:58.338218209 -0400

@@ -40,7 +40,7 @@

 select IF(variable_value - @b2 between 100 and 5000, 'OK', 'FAIL') as Binlog_group_commits 

 from information_schema.global_status where variable_name='Binlog_group_commits';

 Binlog_group_commits

-OK

+FAIL

 select IF(variable_value - @b3 between 1 and 9000, 'OK', 'FAIL')

 from information_schema.global_status where variable_name='Rocksdb_wal_synced';

 IF(variable_value - @b3 between 1 and 9000, 'OK', 'FAIL')

mysqltest: Result length mismatch