MariaDB: add new parameter dr to query callbacks

Signed-off-by: swpd <swpdtz@gmail.com>
MariaDB: remember to remove MariaDB connection context from the thread specific list, otherwise a later attempt to access it will cause segmentation fault

Signed-off-by: swpd <swpdtz@gmail.com>
MariaDB: remove extra case

Signed-off-by: swpd <swpdtz@gmail.com>