sockfd_cache: close socket always when node is crashed

When timeout happens, we cannot reuse the socket for other transfers
because data may remain in its send (or recv) buffer.  We have to
close the socket before making the sockfd_cache reusable.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <tailai.ly@taobao.com>