CLEANUP: listeners: remove unused disable_listener and disable_all_listeners

These ones have never been called, they were referenced by the protocol's
disable_all for some protocols but there are no traces of their use, so
in addition to not being sure the code works, it has never been tested.
Let's remove a bit of complexity starting from there.
diff --git a/include/haproxy/listener.h b/include/haproxy/listener.h
index 3233ad5..e2574e6 100644
--- a/include/haproxy/listener.h
+++ b/include/haproxy/listener.h
@@ -56,13 +56,6 @@
  */
 int enable_all_listeners(struct protocol *proto);
 
-/* This function removes all of the protocol's listener's file descriptors from
- * the polling lists when they are in the LI_READY or LI_FULL states. It is
- * intended to be used as a protocol's generic disable_all() primitive. It puts
- * the listeners into LI_LISTEN, and always returns ERR_NONE.
- */
-int disable_all_listeners(struct protocol *proto);
-
 /* Dequeues all listeners waiting for a resource the global wait queue */
 void dequeue_all_listeners();
 
diff --git a/src/listener.c b/src/listener.c
index 39f5b34..30d12e9 100644
--- a/src/listener.c
+++ b/src/listener.c
@@ -309,23 +309,6 @@
 	HA_SPIN_UNLOCK(LISTENER_LOCK, &listener->lock);
 }
 
-/* This function removes the specified listener's file descriptor from the
- * polling lists if it is in the LI_READY or in the LI_FULL state. The listener
- * enters LI_LISTEN.
- */
-static void disable_listener(struct listener *listener)
-{
-	HA_SPIN_LOCK(LISTENER_LOCK, &listener->lock);
-	if (listener->state < LI_READY)
-		goto end;
-	if (listener->state == LI_READY)
-		fd_stop_recv(listener->rx.fd);
-	MT_LIST_DEL(&listener->wait_queue);
-	listener_set_state(listener, LI_LISTEN);
-  end:
-	HA_SPIN_UNLOCK(LISTENER_LOCK, &listener->lock);
-}
-
 /* This function tries to temporarily disable a listener, depending on the OS
  * capabilities. Linux unbinds the listen socket after a SHUT_RD, and ignores
  * SHUT_WR. Solaris refuses either shutdown(). OpenBSD ignores SHUT_RD but
@@ -498,23 +481,6 @@
 	return ERR_NONE;
 }
 
-/* This function removes all of the protocol's listener's file descriptors from
- * the polling lists when they are in the LI_READY or LI_FULL states. It is
- * intended to be used as a protocol's generic disable_all() primitive. It puts
- * the listeners into LI_LISTEN, and always returns ERR_NONE.
- *
- * Must be called with proto_lock held.
- *
- */
-int disable_all_listeners(struct protocol *proto)
-{
-	struct listener *listener;
-
-	list_for_each_entry(listener, &proto->listeners, rx.proto_list)
-		disable_listener(listener);
-	return ERR_NONE;
-}
-
 /* Dequeues all listeners waiting for a resource the global wait queue */
 void dequeue_all_listeners()
 {