treecompose: Use an external webserver with dynamic port
    
    I was having trouble with imagefactory accessing the content; it
    turned out to be firewalld on the host blocking access to the port.
    
    In the process of debugging that I switched to using an external
    webserver as then I could just strace -p it to see what was going
    on
    
    A nice benefit of ostree trivial-httpd is it dynamically allocates an
    *unused* port.  That way we don't need to hardcode 8000.
    
    This patch changes the kickstart file to use that dynamic port.
    
    Furthermore, I changed the IP address range to match the observed
    range I'm getting here.  However...that may be a local libvirt change.
    
    I need to figure out whether there's a reliable way to communciate the
    host IP address/location into the kickstart we sent to the VM.