Upstream: fixed EOF handling in unbuffered and upgraded modes.
Upstream: fixed EOF handling in unbuffered and upgraded modes.

With level-triggered event methods it is important to specify
the NGX_CLOSE_EVENT flag to ngx_handle_read_event(), otherwise
the event won't be removed, resulting in CPU hog.

Reported by Patrick Wollgast.

hy0kl/nginx,hy0kl/nginx,hy0kl/nginx