refactored client manager to gain more flexibility

protocols/bgp/server/update_sender.go

routingtable/adjRIBIn/adj_rib_in.go

routingtable/adjRIBIn/adj_rib_in_test.go

routingtable/adjRIBOut/adj_rib_out.go

routingtable/client_interface.go

routingtable/client_manager.go

routingtable/client_manager_test.go

routingtable/locRIB/loc_rib.go