main.query_cache_debug failed in buildbot, Query cache is disabled

main.query_cache_debug                   w3 [ fail ]

        Test ended at 2018-02-08 19:56:49

CURRENT_TEST: main.query_cache_debug

mysqltest: At line 371: query 'SEt GLOBAL query_cache_type= DEFAULT' failed: 1924: Query cache is disabled (resize or similar command in progress); repeat this command later

The result from queries just before the failure was:

< snip >

`id` int(10) NOT NULL AUTO_INCREMENT,

`k` int(10) default '0',

PRIMARY KEY (`id`))

ENGINE=MyISAM;

INSERT IGNORE INTO t1 VALUES

(NULL,1),(NULL,8),(NULL,NULL),(NULL,NULL),(NULL,4),(NULL,9),(NULL,7),

(NULL,3),(NULL,NULL),(NULL,2),(NULL,3),(NULL,NULL),(NULL,2),(NULL,7),

(NULL,1),(NULL,2),(NULL,4),(NULL,NULL),(NULL,1),(NULL,1),(NULL,4);

SET GLOBAL query_cache_size= 1024*1024;

SET GLOBAL query_cache_type= 1;

set debug_sync="wait_in_query_cache_store_query SIGNAL parked WAIT_FOR go";

SELECT DISTINCT id FROM t1 WHERE id BETWEEN 5603 AND 16218 ORDER BY k;

set debug_sync="now WAIT_FOR parked";

SET GLOBAL query_cache_type= 0;

set debug_sync="now SIGNAL go";

id

set debug_sync= 'RESET';

DROP TABLE t1;

SEt GLOBAL query_cache_size= DEFAULT;

SEt GLOBAL query_cache_type= DEFAULT;