(ITS#6736) Listener info destroyed too early on shutdown

Full_Name: Hallvard B Furuseth Version: HEAD OS: URL: Submission from: (NULL) (129.240.6.233) Submitted by: hallvard

On shutdown, slapd_daemon_task() calls close_listeners() which destroys slap_listeners[] while other threads may be accessing it. This is not mutex-protected. Valgrind reports freed data accesses in back-monitor and slapd_listener() when they try to read the URLs in the listeners.

Giving HEAD a minimal fix: Stop listening but delay destruction.

If anyone feels like it, the new 'listening' flag probably can be used more intelligently, e.g. by rearranging the use of it and some shutdown flags.