Use the new, double-add protected hook functions

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

src/Akela/Leader.cpp

@@ -78,8 +78,8 @@ namespace Akela {
 
   void
   Leader::begin (void) {
-    event_handler_hook_add (this->eventHandlerHook);
+    event_handler_hook_use (this->eventHandlerHook);
-    loop_hook_add (this->loopHook);
+    loop_hook_use (this->loopHook);
   }
 
   void