Add /session/token_sync POST support
    
    This HTTP call takes the following parameters:
     * user
     * password
     * first_code
     * second_code
     * token (optional)
    
    Using this information, the server will perform token synchronization.
    If the token is not specified, all tokens will be searched for synchronization.
    Otherwise, only the token specified will be searched.
    
    https://fedorahosted.org/freeipa/ticket/4218
    
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>