tokudb.change_column_varbin failed in buildbot with timeout

tokudb.change_column_varbin              w2 [ fail ]  timeout after 900 seconds

        Test ended at 2018-11-06 09:20:42

Test case timeout after 900 seconds

== /dev/shm/var/2/log/change_column_varbin.log == 

ALTER TABLE t CHANGE COLUMN a a VARBINARY(386);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(386);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(387);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(387);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(388);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(388);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(389);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(389);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(390);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(390);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(391);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(391);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(392);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(392);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(393);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(393);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(394);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(394);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(395);

ALTER TABLE t CHANGE COLUMN a a VARBINARY(395);

 == /dev/shm/var/2/tmp/analyze-timeout-mysqld.1.err ==

mysqltest: Could not open connection 'default': 2013 Lost connection to MySQL server at 'handshake: reading inital communication packet', system error: 104