(ITS#8484) tlsm_register_shutdown_callonce needs to be reinitialized

[soohoon.lee@f5.com]

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.