grpcclient: set timeout for ping request

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

frontend/gateway/grpcclient/client.go

@@ -28,6 +28,8 @@ type GrpcClient interface {
 }
 
 func New(ctx context.Context, opts map[string]string, session, product string, c pb.LLBBridgeClient, w []client.WorkerInfo) (GrpcClient, error) {
+	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
+	defer cancel()
 	resp, err := c.Ping(ctx, &pb.PingRequest{})
 	if err != nil {
 		return nil, err