Problem: check for item.fd causes zloop_poller regression

Solution: fix the check for the socket.
This regression happens when using zloop with zmq_pollitem_it with
only file descriptors registerted through zloop_poller.

src/zmq.cpp

@@ -834,7 +834,7 @@ inline int zmq_poller_poll (zmq_pollitem_t *items_, int nitems_, long timeout_)
         for (int j = j_start; j < found_events; ++j) {
             if (
                 (items_[i].socket && items_[i].socket == events[j].socket) ||
-                (!(items_[i].socket || items_[j].socket) && items_[i].fd == events[j].fd)
+                (!items_[i].socket && items_[i].fd == events[j].fd)
             ) {
                 items_[i].revents = events[j].events & items_[i].events;
                 if (!repeat_items) {