func_periodic_hook: Add hangup step to avoid timeout

func_periodic_hook does not hangup after playback, relying on hangup
which keeps the channel alive longer than necessary.

Resolves: #325

funcs/func_periodic_hook.c

@@ -487,6 +487,8 @@ static int load_module(void)
 			"Answer", "", NULL, AST_MODULE);
 	res |= ast_add_extension(context_name, 1, beep_exten, 2, "", "",
 			"Playback", "beep", NULL, AST_MODULE);
+	res |= ast_add_extension(context_name, 1, beep_exten, 3, "", "",
+			"Hangup", "", NULL, AST_MODULE);
 
 	res |= ast_custom_function_register_escalating(&hook_function, AST_CFE_BOTH);