Events: fixed EPOLLRDHUP with FIONREAD (ticket #2367). When reading exactly rev->available bytes, rev->available might become 0 after FIONREAD usage introduction in efd71d49bde0. On the next call of ngx_readv_chain() on systems with EPOLLRDHUP this resulted in return without any actions, that is, with rev->ready set, and this in turn resulted in no timers set in event pipe, leading to socket leaks. Fix is to reset rev->ready in ngx_readv_chain() when returning due to rev->available being 0 with EPOLLRDHUP, much like it is already done in ngx_unix_recv(). This ensures that if rev->available will become 0, on systems with EPOLLRDHUP support appropriate EPOLLRDHUP-specific handling will happen on the next ngx_readv_chain() call. While here, also synced ngx_readv_chain() to match ngx_unix_recv() and reset rev->ready when returning due to rev->available being 0 with kqueue. This is mostly cosmetic change, as rev->ready is anyway reset when rev->available is set to 0.

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