show_explain_ps fails in buildbot after a certain sequence of tests

main.show_explain_ps                     w4 [ fail ]

        Test ended at 2014-11-28 04:05:02

CURRENT_TEST: main.show_explain_ps

--- /mnt/buildbot/build/mariadb-10.1.2/mysql-test/r/show_explain_ps.result	2014-11-27 20:27:48.000000000 +0200

+++ /mnt/buildbot/build/mariadb-10.1.2/mysql-test/r/show_explain_ps.reject	2014-11-28 04:05:02.000000000 +0200

@@ -25,5 +25,4 @@

 from performance_schema.events_waits_history_long 

 where event_name='wait/synch/cond/sql/show_explain';

 event_name

-wait/synch/cond/sql/show_explain

 drop table t0;

mysqltest: Result length mismatch

perl  ./mtr --noreorder main.mysqld--defaults-file main.mysqld--help,unix main.mysqld_option_err main.mysqlhotcopy_myisam main.mysqlshow main.mysqlslap main.mysqltest_256 main.mysqltest_cont_on_error main.mysqltest_ps main.select_debug main.select_found main.select_jcl6 main.select_safe main.servers main.set_statement main.set_statement_debug main.set_statement_profiling main.show_explain_ps

perl ./mtr --noreorder main.join_outer main.join_outer_jcl6 main.query_cache main.query_cache_debug archive.archive_plugin csv.csv csv.csv_alter_table csv.csv_not_null handler.aria handler.disconnect_4480 handler.heap handler.myisam heap.heap main.alter_table_mdev539_maria main.analyze main.bad_frm_crash_5029 main.check main.client_xml main.constraints main.contributors main.count_distinct main.create-uca main.create_not_windows main.ctype_ascii main.ctype_big5 main.ctype_binary main.ctype_collate main.ctype_cp1250_ch main.ctype_cp1251 main.ctype_create main.ctype_errors main.ctype_eucjpms main.ctype_filename main.ctype_gb2312 main.ctype_gbk main.ctype_hebrew main.ctype_many main.ctype_mb main.ctype_tis620 main.ctype_ucs main.ctype_ujis main.ctype_ujis_ucs2 main.ctype_utf16 main.ctype_utf16le main.ctype_utf8mb4_heap main.ddl_i18n_utf8 main.delayed main.delete_returning main.derived_opt main.derived_view main.dirty_close main.drop main.drop-no_root main.execution_constants main.explain main.failed_auth_3909 main.features main.file_contents main.filesort_debug main.fix_priv_tables main.flush_table main.fulltext main.fulltext2 main.fulltext3 main.fulltext_distinct main.func_des_encrypt main.func_encrypt_nossl main.func_if main.func_in main.func_isnull main.func_like main.func_math main.func_misc main.func_system main.func_time main.func_timestamp main.function_defaults_notembedded main.gis-debug main.gis-precise main.index_merge_myisam main.information_schema2 main.information_schema_db main.information_schema_routines main.kill main.lock_multi_bug38691 main.log_slow main.log_tables_debug main.lowercase_fs_off main.lowercase_table5 main.mdev316 main.mdev375 main.merge main.merge_debug main.metadata main.mix2_myisam main.mix2_myisam_ucs2 main.mrr_icp_extra main.myisam-system main.myisam_debug main.myisam_explain_non_select_all main.myisam_icp main.myisam_icp_notembedded main.myisam_mrr main.myisam_optimize main.myisampack main.mysql main.mysql-bug41486 main.mysql-bug45236 main.mysql5613mysql main.mysql_comments main.mysql_cp932 main.mysql_locale_posix main.mysql_not_windows main.mysql_protocols main.mysql_tzinfo_to_sql_symlink main.mysql_upgrade_no_innodb main.mysqladmin main.mysqld--defaults-file main.mysqld--help main.mysqld_option_err main.mysqlhotcopy_myisam main.mysqlslap main.mysqltest_ps main.no_binlog main.outfile main.outfile_loaddata main.plugin_vars main.processlist main.profiling main.ps_10nestset main.ps_11bugs main.ps_2myisam main.query_cache_notembedded main.query_cache_ps_no_prot main.query_cache_ps_ps_prot main.query_cache_with_views main.read_only main.select_debug main.select_found main.select_jcl6 main.select_safe main.servers main.show_explain_ps