Thanks for reporting and researching! Looks like this isn't going to be fixed for 10.1, but you can use a SSH tunnel with 10.1 or alternatively upgrade MariaDB to a newer version.
- Bug#956401: mariadb-server: --ssl-verify-server-cert f... Humberto Flores III
- Bug#956401: mariadb-server: --ssl-verify-server-c... Humberto Flores III
- Bug#956401: mariadb-server: --ssl-verify-serv... Otto Kekäläinen