Fix segfault on shut down of SQL queue manager in rare case where registration…

Fix segfault on shut down of SQL queue manager in rare case where registration cleanup is firing at the same time the queue manager is shutting down.

src/switch_core_sqldb.c

@@ -3251,14 +3251,13 @@ void switch_core_sqldb_stop(void)
 
 	switch_event_unbind_callback(core_event_handler);
 
-	switch_core_sqldb_stop_thread();
-
-
 	if (sql_manager.db_thread && sql_manager.db_thread_running) {
 		sql_manager.db_thread_running = -1;
 		switch_thread_join(&st, sql_manager.db_thread);
 	}
 
+	switch_core_sqldb_stop_thread();
+
 	switch_cache_db_flush_handles();
 	sql_close(0);
 }