Resolve "A change confirm updates the network element multiple times"

controller/interfaces/change/change.go

controller/interfaces/transport/transport.go

controller/mocks/Change.go

controller/mocks/Transport.go

controller/northbound/server/networkElement.go

controller/nucleus/change.go

controller/nucleus/gnmi_transport.go

controller/nucleus/gnmi_transport_test.go

controller/nucleus/util/gnmi/notification.go