NSS: re-register NSS_Shutdown callback

Original upstream comment:
"""
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.
"""

Sent-By: soohoon.lee@f5.com
Original-Name: soohoon-lee-160823.patch
Upstream-ITS: 8484

diff --git a/libraries/libldap/tls_m.c b/libraries/libldap/tls_m.c
index cdf7f8e..cf05914 100644
--- a/libraries/libldap/tls_m.c
+++ b/libraries/libldap/tls_m.c
@@ -1145,6 +1145,8 @@ tlsm_auth_cert_handler(void *arg, PRFileDesc *fd,
 	return ret;
 }
 
+static PRCallOnceType tlsm_register_shutdown_callonce = {0,0};
+
 static SECStatus
 tlsm_nss_shutdown_cb( void *appData, void *nssData )
 {
@@ -1157,10 +1159,15 @@ tlsm_nss_shutdown_cb( void *appData, void *nssData )
 		SECMOD_DestroyModule( pem_module );
 		pem_module = NULL;
 	}
+
+	/* init callonce so it can be armed again for cases like persistent daemon with LDAP_OPT_X_TLS_NEWCTX */
+	tlsm_register_shutdown_callonce.initialized = 0;
+	tlsm_register_shutdown_callonce.inProgress = 0;
+	tlsm_register_shutdown_callonce.status = 0;
+
 	return rc;
 }
 
-static PRCallOnceType tlsm_register_shutdown_callonce = {0,0};
 static PRStatus PR_CALLBACK
 tlsm_register_nss_shutdown_cb( void )
 {