code: public boolean inactiveSetChanged(Collection<Host> hostsUp, Collection<Host> hostsDown) {
  		
  		boolean newInactiveHostsFound = false;
  		
  		// Check for condition 1. 
  		for (Host hostDown : hostsDown) {
  			if (activeHosts.contains(hostDown)) {
  				newInactiveHostsFound = true;
  				break;
  			}
  		}
  		
  		// Check for condition 2. 
  		Set<Host> prevActiveHosts = new HashSet<Host>(activeHosts);
  		prevActiveHosts.removeAll(hostsUp);
  		
  		newInactiveHostsFound = !prevActiveHosts.isEmpty();
  		
  		return newInactiveHostsFound;
  	}
docs: This check is more involved than the active set check. Here we 2 conditions to check for
  
  1. We could have new hosts that were in the active set and have shown up in the inactive set.
  2. We can also have the case where hosts from the active set have disappeared and also not in the provided inactive set.
  This is where we have simply forgotten about some active host and that it needs to be shutdown
  
  @param hostsUp
  @param hostsDown
  @return true/false indicating whether we have a host that has been shutdown