Replace formatted errors when unneeded

Signed-off-by: John Hwang <John.F.Hwang@gmail.com>

checkpoint.go

@@ -3,6 +3,7 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"strconv"
@@ -91,11 +92,11 @@ func setPageServer(context *cli.Context, options *libcontainer.CriuOpts) {
 	if psOpt := context.String("page-server"); psOpt != "" {
 		addressPort := strings.Split(psOpt, ":")
 		if len(addressPort) != 2 {
-			fatal(fmt.Errorf("Use --page-server ADDRESS:PORT to specify page server"))
+			fatal(errors.New("Use --page-server ADDRESS:PORT to specify page server"))
 		}
 		portInt, err := strconv.Atoi(addressPort[1])
 		if err != nil {
-			fatal(fmt.Errorf("Invalid port number"))
+			fatal(errors.New("Invalid port number"))
 		}
 		options.PageServer = libcontainer.CriuPageServerInfo{
 			Address: addressPort[0],
@@ -114,7 +115,7 @@ func setManageCgroupsMode(context *cli.Context, options *libcontainer.CriuOpts)
 		case "strict":
 			options.ManageCgroupsMode = libcontainer.CRIU_CG_MODE_STRICT
 		default:
-			fatal(fmt.Errorf("Invalid manage cgroups mode"))
+			fatal(errors.New("Invalid manage cgroups mode"))
 		}
 	}
 }