Use correct error type when handling federated identity credential deletion (#3913)

* Use correct error type when handling federated identity credential deletion

* Use 'errors.As' instead of type assertion

pkg/cluster/delete.go

@@ -6,12 +6,14 @@ package cluster
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
 	"sort"
 	"strings"
 	"time"
 
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore"
 	"github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/msi/armmsi"
 	"github.com/Azure/azure-sdk-for-go/sdk/storage/azblob"
 	mgmtnetwork "github.com/Azure/azure-sdk-for-go/services/network/mgmt/2020-08-01/network"
@@ -425,13 +427,12 @@ func (m *manager) deleteFederatedCredentials(ctx context.Context) error {
 				&armmsi.FederatedIdentityCredentialsClientDeleteOptions{},
 			)
 			if err != nil {
-				cloudErr := err.(*api.CloudError)
-
-				if cloudErr.StatusCode == http.StatusNotFound {
-					m.log.Errorf("federated identity credentials not found for %s: %v", identity.ResourceID, cloudErr.Error())
+				var respErr *azcore.ResponseError
+				if errors.As(err, &respErr); respErr.StatusCode == http.StatusNotFound {
+					m.log.Errorf("federated identity credentials not found for %s: %v", identity.ResourceID, err.Error())
 					continue
 				} else {
-					return fmt.Errorf("failed to delete federated identity credentials for %s: %v", identity.ResourceID, cloudErr.Error())
+					return fmt.Errorf("failed to delete federated identity credentials for %s: %v", identity.ResourceID, err.Error())
 				}
 			}
 		}