Make sure that openid redirects back to root on no request
    
    If there is no request, we redirect to self.basepath, but if Ipsilon is mounted
    to the root (/), basepath is set to None.
    Sending a HTTPRedirect(None) redirects back to the current page.
    So this change makes OpenID send the user to / in this case.
    
    Fixes: #225
    Signed-off-by: Patrick Uiterwijk <puiterwijk@redhat.com>
    Reviewed-by: Randy Barlow <randy@electronsweatshop.com>
    Reviewed-by: Howard Johnson <merlin@merlinthp.org>