tokudb.i_s_tokudb_locks_released is unstable

Similar to DB-964, this failure is likely due to very short lock timeouts and slow machine.

5.6:
https://github.com/georgelorchpercona/percona-server/tree/ps-5.6-TokuDB-MTR
http://jenkins.percona.com/view/PS%205.6/job/percona-server-5.6-param/1103/
https://github.com/percona/percona-server/pull/433

5.7:
https://github.com/georgelorchpercona/percona-server/tree/ps-5.7-TokuDB-MTR
http://jenkins.percona.com/view/5.7/job/mysql-5.7-param/129/
https://github.com/percona/percona-server/pull/434

Seems still somewhat unstable:

Try #2, combined with same/similar fix for DB-964:
5.6:
https://github.com/georgelorchpercona/percona-server/tree/ps-5.6-DB-964
http://jenkins.percona.com/view/PS%205.6/job/percona-server-5.6-param/1197/
https://github.com/percona/percona-server/pull/623

5.7:
https://github.com/georgelorchpercona/percona-server/tree/ps-5.7-DB-964
http://jenkins.percona.com/view/5.7/job/mysql-5.7-param/214/
https://github.com/percona/percona-server/pull/624