rocksdb.autoinc_vars_thread fails in buildbot with wrong result

rocksdb.autoinc_vars_thread              w1 [ fail ]

        Test ended at 2018-06-22 15:55:53

CURRENT_TEST: rocksdb.autoinc_vars_thread

--- /usr/share/mysql-test/plugin/rocksdb/rocksdb/r/autoinc_vars_thread.result	2018-06-22 14:42:26.000000000 +0000

+++ /dev/shm/var/1/log/autoinc_vars_thread.reject	2018-06-22 15:55:53.212777446 +0000

@@ -25,6 +25,8 @@

 SET debug_sync='now SIGNAL go2';

 connection default;

 connection con1;

+Warnings:

+Warning	1639	debug sync point wait timed out

 connection con2;

 connection default;

 SET debug_sync='RESET';

mysqltest: Result length mismatch

 - found 'core.5352' (0/0)

Trying 'dbx' to get a backtrace

gdb not found, cannot get the stack trace

Compressed file /dev/shm/var/1/log/rocksdb.autoinc_vars_thread/mysqld.1/data/core.5352

 - found 'core.5276' (1/0)

Trying 'dbx' to get a backtrace

gdb not found, cannot get the stack trace

Compressed file /dev/shm/var/1/log/rocksdb.autoinc_vars_thread/mysqld.1/data/core.5276

 - skipping '/dev/shm/var/1/log/rocksdb.autoinc_vars_thread/'