whois(1): Fix potential double-close and logic mistakes

Close the fd the poll error was detected on, rather than the last opened fd, to
fix the double-close.

Use -1 to make it explict which int variables no longer own socket file
descriptors.

Actually shrink, rather than grow, the poll timeout to match comment.

Reported by: Coverity
CID: 1304860, 1305616
Sponsored by: EMC / Isilon Storage Division