add the systemd-modules-load test to upstream repo
    
    The systemd-modules-load service is available in various Fedoras
    and RHELs, so it makes sense to run the TC in upstream testing too.
    
    There are no changes in the TC functionality, except for the kernel
    module (downstream: nf_conntrack_ipv4 vs. upstream: nf_conntrack_pptp)
    that is used.
    
    Moving the downstream TC to upstream repo.