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>
add missing result codes to sd_strerror

This also uses array to look up the error message for a bit better
performance.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
use sd_strerror to print error reason

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
sheep: fix error message of do_epoch_log_read

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
sheep: don't recovery from local when epoch equals sys->epoch

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
sheep: recover from local if possible

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Revert dual nic support

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>