libykclient should ignore validation servers that it can't connect to

[alexjfisher]

I've been testing pam_yubico's urllist option and have noticed that if a validation server isn't running (ie service httpd stop), validation fails. I think the idea is that remaining servers should be able to respond.

Pull request with a possible fix to follow.

Thanks,
Alex

[klali]

Good catch, thank you!

I'm pushing a test for this and a slightly different fix where we skip over any response that isn't CURLE_OK.

/klas