(ITS#8484) tlsm_register_shutdown_callonce needs to be reinitialized

Full_Name: soohoon lee Version: HEAD OS: linux 7.2 URL: ftp://ftp.openldap.org/incoming/soohoon-lee-160823.patch Submission from: (NULL) (50.205.70.164)

When there's a persistent daemon for auth and it sets LDAP_OPT_X_TLS_NEWCTX, it fails to auth at third login.

1. everything is good and destroyed after use but tlsm_register_shutdown_callonce.initialized=1. 2. still good but because tlsm_register_shutdown_callonce.initialized==1, it fails to register shutdown function. so pem_module is not destroyed at the end. 3. pem_module is not NULL so it's not initialized again and not added to modules list. And Login fails.