Protection from stale write events in epoll.
Protection from stale write events in epoll.

Stale write event may happen if epoll_wait() reported both read and write
events, and processing of the read event closed descriptor.

Patch by Yichun Zhang (agentzh).

firebase/nginx,hy0kl/nginx,hy0kl/nginx,firebase/nginx,hy0kl/nginx,firebase/nginx,firebase/nginx