BUG#21833 (Prepare_commit_mutex not locked and unlocked under same condition): Adding condition to ensure that mutex are locked and unlocked under same condition.
BUG#21833 (Prepare_commit_mutex not locked and unlocked under same condition):
Adding condition to ensure that mutex are locked and unlocked
under same condition.

davidl-zend/zenddbi,davidl-zend/zenddbi,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,flynn1973/mariadb-aix,davidl-zend/zenddbi,flynn1973/mariadb-aix,ollie314/server,davidl-zend/zenddbi,ollie314/server,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,davidl-zend/zenddbi,davidl-zend/zenddbi,slanterns/server,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,davidl-zend/zenddbi,ollie314/server,ollie314/server,flynn1973/mariadb-aix,ollie314/server,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,natsys/mariadb_10.2,davidl-zend/zenddbi,flynn1973/mariadb-aix