MDEV-10258 - Valgrind warnings in buildbot after a set of mroonga tests
MDEV-10258 - Valgrind warnings in buildbot after a set of mroonga tests

Fixed memory leak when mroonga fails to open index files.
Memory leak was detected by valgrind when running
mroonga/storage.repair_table_no_index_file.

flynn1973/mariadb-aix,flynn1973/mariadb-aix,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,flynn1973/mariadb-aix,flynn1973/mariadb-aix,flynn1973/mariadb-aix,flynn1973/mariadb-aix,ollie314/server,flynn1973/mariadb-aix,natsys/mariadb_10.2,ollie314/server,ollie314/server,ollie314/server,ollie314/server,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,flynn1973/mariadb-aix,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,ollie314/server,ollie314/server,ollie314/server,natsys/mariadb_10.2,ollie314/server