Don't report distance twice if same system is centre/history
Don't report distance twice if same system is centre/history

Slight improvement

mwerle/EDDiscovery,vendolis/EDDiscovery,jgoode/EDDiscovery,jeoffman/EDDiscovery,jthorpe4/EDDiscovery,mwerle/EDDiscovery,jgoode/EDDiscovery,jeoffman/EDDiscovery,vendolis/EDDiscovery