Revert "Use callback-driven approach to block renegotiations."

This reverts commit 406ae1ba5a.

src/common/compat_libevent.h

@@ -46,9 +46,6 @@ void tor_event_free(struct event *ev);
 
 typedef struct periodic_timer_t periodic_timer_t;
 
-int tor_event_base_once(void (*cb)(evutil_socket_t, short, void *),
-                        void *arg, struct timeval *timer);
-
 periodic_timer_t *periodic_timer_new(struct event_base *base,
              const struct timeval *tv,
              void (*cb)(periodic_timer_t *timer, void *data),