- EV_CLOSED is EPOLLRDHUP in epoll
- EPOLLRDHUP reported w/o EPOLLHUP if the socket closed with shutdown(SHUT_WR)
- EPOLLRDHUP reported w/ EPOLLHUP if the socket closed with close()
so in this case epoll backend will detect this event as error
(EV_READ|EV_WRITE), since the epoll_ctl() will return EPOLLRDHUP with
EPOLLHUP set, but this is not correct, let's fix this.
Fixes: #984
(cherry picked from commit 972b456bf60e9a2f550ec45a14921c06e252c793)