Check source type directly, not via DBus
    
    Not all payloads are available via DBus in RHEL 8 Anaconda,
    so use the payload instance directly when checking payload type
    in the Connect to Red Hat spokes. Also in some cases the payload
    type could be None instead of a string, so handle that as well.
    
    This should fix the issue with RHV, which uses the liveimg payload,
    which is not available via DBus on RHEL 8, leading to a crash.
    
    Resolves: rhbz#1941578