ZMQII-1: fix for devpoll, kqueue & poll

src/devpoll.cpp

@@ -54,10 +54,11 @@ zmq::devpoll_t::devpoll_t ()
 
 zmq::devpoll_t::~devpoll_t ()
 {
+    worker.stop ();
+
     //  Make sure there are no fds registered on shutdown.
     zmq_assert (load.get () == 0);
 
-    worker.stop ();
     close (devpoll_fd);
 }
 

src/kqueue.cpp

@@ -42,10 +42,11 @@ zmq::kqueue_t::kqueue_t ()
 
 zmq::kqueue_t::~kqueue_t ()
 {
+    worker.stop ();
+
     //  Make sure there are no fds registered on shutdown.
     zmq_assert (load.get () == 0);
 
-    worker.stop ();
     close (kqueue_fd);
 }
 

src/poll.cpp

@@ -52,10 +52,10 @@ zmq::poll_t::poll_t () :
 
 zmq::poll_t::~poll_t ()
 {
+    worker.stop ();
+
     //  Make sure there are no fds registered on shutdown.
     zmq_assert (load.get () == 0);
-
-    worker.stop ();
 }
 
 zmq::handle_t zmq::poll_t::add_fd (fd_t fd_, i_poll_events *events_)