unix: fix error check when closing process pipe fd
unix: fix error check when closing process pipe fd

uv__close() does not set errno, it returns the error.  It also never
returns EINTR, it always maps it to EINPROGRESS.

PR-URL: https://github.com/libuv/libuv/pull/512
Reviewed-By: Saúl Ibarra Corretgé <8a7991f6950ea189abf159d6ec98d2fcc13dc5f6@gmail.com>

unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso