Add Cache-Control header to prevent browser caching of SAML auth location
    
    We should prevent browser caching of the SAML auth location that we
    configure for an SP. This can be easily done by adding the following
    directive to that location in the httpd config:
    
        Header append Cache-Control "no-cache"
    
    https://fedorahosted.org/ipsilon/ticket/81
    
    Signed-off-by: Nathan Kinder <nkinder@redhat.com>
    Reviewed-by: Rob Crittenden <rcritten@redhat.com>