Fix Go vet errors for master golang

Co-authored-by: Rajalakshmi-Girish <rajalakshmi.girish1@ibm.com>
Co-authored-by: Abhishek Kr Srivastav <Abhishek.kr.srivastav@ibm.com>

test/utils/density_utils.go

@@ -18,6 +18,7 @@ package utils
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strings"
 	"time"
@@ -99,7 +100,7 @@ func VerifyLabelsRemoved(c clientset.Interface, nodeName string, labelKeys []str
 	}
 	for _, labelKey := range labelKeys {
 		if node.Labels != nil && len(node.Labels[labelKey]) != 0 {
-			return fmt.Errorf("Failed removing label " + labelKey + " of the node " + nodeName)
+			return errors.New("Failed removing label " + labelKey + " of the node " + nodeName)
 		}
 	}
 	return nil