control: close directory watch on quick shutdown (fix SIGABRT at exit)

Control::handle_shutdown() closes m_directory_events (the inotify directory
watch) only in the normal-shutdown branch (!m_shutdownQuick). On a quick
shutdown (SIGTERM -> receive_quick_shutdown) the m_shutdownQuick branch skips
it, so the watch stays registered in the poll. ~Control() then destroys the
still-open directory_events and Event::~Event()'s assert(m_poll_event == nullptr)
(added with the 0.16.13 poll/event rework) aborts:

    main -> Control::~Control() -> ~directory_events -> ~Event() -> abort

Close it in Control::cleanup() instead, which runs on every shutdown path after
the session is saved; close() is idempotent, so the normal path that already
closed it in handle_shutdown() is unaffected.

Reproducible: configure a directory.watch.added watch, then SIGTERM the client
-> SIGABRT (core in Event::~Event); SIGINT (normal shutdown) is clean. With this
change SIGTERM exits cleanly too.

src/control.cc

@@ -88,6 +88,15 @@ Control::cleanup() {
   if(!display::Canvas::daemon())
     m_inputStdin->remove();
 
+  // Close the directory watch (inotify) Event on every shutdown path.
+  // handle_shutdown() only closes it on a normal shutdown; a quick shutdown
+  // (SIGTERM -> receive_quick_shutdown) takes the m_shutdownQuick branch and
+  // skips it, leaving directory_events registered in the poll. ~Control() would
+  // then destroy it while still open and trip the Event::~Event() assert
+  // (m_poll_event == nullptr) -> SIGABRT. close() is idempotent (no-op when the
+  // normal path already closed it).
+  m_directory_events->close();
+
   if (scgi_thread::thread()->is_active())
     scgi_thread::thread()->stop_thread_wait();