Problem:
========
During mysqld initialization, if the number of GTIDs added since
that last purge of the mysql.gtid_slave_pos tables is greater than
or equal to the –-gtid-cleanup-batch-size value, a race condition
can occur. Specifically, the binlog background thread will submit
the bg_gtid_delete_pending job to the mysql handle manager; however,
the mysql handle manager may not be initialized, leading to crashes.

Solution:
========
Force the mysql handle manager to initialize/start before the binlog
background thread is created.

Reviewed By:
============
Andrei Elkin <andrei.elkin@mariadb.com>