This should also fix the MariaDB 10.2.2 bug
MDEV-13826 CREATE FULLTEXT INDEX on encrypted table fails.
MDEV-12634 FIXME: Modify innodb-index-online, innodb-table-online
so that they will write and read merge sort files. InnoDB 5.7
introduced some optimizations to avoid using the files for small tables.
Many collation test results have been adjusted for MDEV-10191.
Introduce innodb_encrypt_log.combinations and prove that
the encryption and decryption take place during both
online ADD INDEX (WL#5266) and online table-rebuilding ALTER (WL#6625).