install-scripts: avoid using --list with chkconfig
    
    This option does not behave properly in F15 as chkconfig does not list services
    moved to use systemd service files.
    
    Plus there are more direct ways than parsing its output, which are more
    reliable.
    
    Also just testing for the availability of the service calling 'chkconfig name'
    is enough.
    
    https://fedorahosted.org/freeipa/ticket/1206