ipa_selinux: Put SELinux map order related variables into structure
    
    Small change to make the code more readable. The relation between
    order, order_array and order_count is more obvious when they
    are grouped in structure.
    
    resolves:
    https://fedorahosted.org/sssd/ticket/2304
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>