test: Fix memory leak of asynctest
test: Fix memory leak of asynctest

ASYNC_init_thread() will be called automatically by ASYNC_start_job(),
so ASYNC_cleanup_thread() must be called at last, otherwise it will
cause memory leak.

Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>

Reviewed-by: Paul Dale <ddec78389666b4f7c9b4d110380c848489a3e4aa@openssl.org>
Reviewed-by: David von Oheimb <fbbca6c63636e78e7034aaf1b4aa3a9736383192@siemens.com>
Reviewed-by: Hugo Landau <ce9fa1e55a72fc9b85dd06e47ea2c07848fb7d2c@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16703)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl