ensure we close the grpc stream (#1098)

* ensure we close the grpc stream

* use g.Close

* use closed bool flag for checking connection close

grpc.go

@@ -211,6 +211,7 @@ func (g *grpcClient) stream(ctx context.Context, node *registry.Node, req client
 	if opts := g.getGrpcCallOptions(); opts != nil {
 		grpcCallOptions = append(grpcCallOptions, opts...)
 	}
+
 	st, err := cc.NewStream(ctx, desc, methodToGRPC(req.Service(), req.Endpoint()), grpcCallOptions...)
 	if err != nil {
 		return nil, errors.InternalServerError("go.micro.client", fmt.Sprintf("Error creating stream: %v", err))