Kill module unloading support
    
    The whole concept is unfixably broken:
    
    Some kernel modules are used by both IPv4 and IPv6 netfilter and the
    algorithm has no way to identify this situation. Therefore if iptables
    and ip6tables services are restarted in parallel, one's module unloading
    tends to stomp onto the other's attempt at loading rules.
    
    Another problem is with OVS: iptables service unloading conntrack
    modules breaks a running OVS instance.