Ticket 50344 - tidy rpm vs build systemd flag handling
    
    Bug Description: In rpm builds we would read with_systemd from
    defaults.inf, which has a diffeent value to hand-building. AS
    a result this caused as issue in dscontainer on opensuse where
    it believed systemd was present.
    
    Fix Description: Simplify the systemd handling to a single flag
    which is possible to override in a container env.
    
    https://pagure.io/389-ds-base/issue/50344
    
    Author: William Brown <william@blackhats.net.au>
    
    Review by: ???