gossip: remove cullNetwork,closeClient
gossip: remove cullNetwork,closeClient

It is only safe for these methods to be called from manage(), and they
are not used elsewhere, so just remove them.

arjun4084346/cockroach,sunya123/cockroach,glycerine/cockroach,petermattis/cockroach,maxlang/cockroach,petermattis/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,cockroachdb/cockroach,vivekmenezes/cockroach,arjun4084346/cockroach,arjun4084346/cockroach,petermattis/cockroach,cockroachdb/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,glycerine/cockroach,maxlang/cockroach,cockroachdb/cockroach,cockroachdb/cockroach,paperstreet/cockroach,sunya123/cockroach,vaibhavarora/cockroach,maxlang/cockroach,cockroachdb/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,petermattis/cockroach,sunya123/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,veteranlu/cockroach,sunya123/cockroach,sunya123/cockroach,cockroachdb/cockroach,sunya123/cockroach,paperstreet/cockroach,glycerine/cockroach,petermattis/cockroach,glycerine/cockroach,vivekmenezes/cockroach,glycerine/cockroach,cockroachdb/cockroach,maxlang/cockroach,paperstreet/cockroach,sunya123/cockroach,petermattis/cockroach,arjun4084346/cockroach,arjun4084346/cockroach,glycerine/cockroach,petermattis/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,maxlang/cockroach,sunya123/cockroach,veteranlu/cockroach,veteranlu/cockroach,maxlang/cockroach,glycerine/cockroach,vivekmenezes/cockroach,vaibhavarora/cockroach,arjun4084346/cockroach,vaibhavarora/cockroach,glycerine/cockroach,maxlang/cockroach,paperstreet/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,paperstreet/cockroach,vivekmenezes/cockroach,paperstreet/cockroach,vivekmenezes/cockroach,vaibhavarora/cockroach,petermattis/cockroach,vaibhavarora/cockroach,arjun4084346/cockroach,veteranlu/cockroach,cockroachdb/cockroach,arjun4084346/cockroach,maxlang/cockroach