main.pool_of_threads fails in buildbot on the new valgrind builder

main.pool_of_threads                     w22 [ fail ]

        Test ended at 2016-12-26 15:28:25

CURRENT_TEST: main.pool_of_threads

Could not execute 'check-testcase' before testcase 'main.pool_of_threads' (res: 1):

mysqltest: Logging to '/dev/shm/var/22/tmp/check-mysqld_1.log'.

mysqltest: Results saved in '/dev/shm/var/22/tmp/check-mysqld_1.result'.

mysqltest: Connecting to server localhost:16460 (socket /dev/shm/var/tmp/22/mysqld.1.sock) as 'root', connection 'default', attempt 0 ...

mysqltest: Could not open connection 'default': 2013 Lost connection to MySQL server at 'handshake: reading inital communication packet', system error: 110

not ok

mysqltest failed but provided no output