Epoll ET setting lost with multiple events for same fd

After two or more events have been registered for the same file
descriptor using EV_ET, if one of the events is deleted, then the
epoll_ctl() call issued by libevent drops the EPOLLET flag resulting in
level triggered notifications.

[ azat: use existing "et" in the evmap_io_del_() ]

epoll.c

@@ -401,11 +401,14 @@ epoll_nochangelist_del(struct event_base *base, evutil_socket_t fd,
 	ch.old_events = old;
 	ch.read_change = ch.write_change = ch.close_change = 0;
 	if (events & EV_WRITE)
-		ch.write_change = EV_CHANGE_DEL;
+		ch.write_change = EV_CHANGE_DEL |
+		    (events & EV_ET);
 	if (events & EV_READ)
-		ch.read_change = EV_CHANGE_DEL;
+		ch.read_change = EV_CHANGE_DEL |
+		    (events & EV_ET);
 	if (events & EV_CLOSED)
-		ch.close_change = EV_CHANGE_DEL;
+		ch.close_change = EV_CHANGE_DEL |
+		    (events & EV_ET);
 
 	return epoll_apply_one_change(base, base->evbase, &ch);
 }

evmap.c

@@ -393,7 +393,8 @@ evmap_io_del_(struct event_base *base, evutil_socket_t fd, struct event *ev)
 
 	if (res) {
 		void *extra = ((char*)ctx) + sizeof(struct evmap_io);
-		if (evsel->del(base, ev->ev_fd, old, res, extra) == -1) {
+		if (evsel->del(base, ev->ev_fd,
+			old, (ev->ev_events & EV_ET) | res, extra) == -1) {
 			retval = -1;
 		} else {
 			retval = 1;