branches/5.1: Use btr_free_root() instead of fseg_free() for the fix of bug #48469, because fseg_free() is not defined in the zip branch. And we could save one mini-trasaction started by fseg_free().
branches/5.1: Use btr_free_root() instead of fseg_free() for
the fix of bug #48469, because fseg_free() is not defined
in the zip branch. And we could save one mini-trasaction started
by fseg_free().

Approved by Marko.


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