Fix a domain exception

Fixes T8538. The `$config` property is not declared on the `PhutilDaemonHandle` class.

Auditors: epriestley

src/daemon/PhutilDaemonHandle.php

@@ -11,6 +11,7 @@ final class PhutilDaemonHandle extends Phobject {
   private $overseer;
   private $daemonClass;
   private $argv;
+  private $config;
   private $pid;
   private $daemonID;
   private $deadline;