Errors from socket.connect() should be treated the same way as async failures.

Errors from socket.connect() should be treated the same way as async failures.

On freebsd non-blocking connect() may return certain errors (such as
ECONNREFUSED from localhost) immediately instead of returning EINPROGRESS
and then giving the error later.

Also improve the test for ipv6 compatibility, since freebsd returns a different
error than other platforms when ipv6 is not available.