registry/storage/driver/azure: fix storage path to use leading slash

this keeps backwards compatibility with pre-v3 registries.

registry/storage/driver/azure/azure.go

@@ -404,20 +404,9 @@ func (d *driver) listBlobs(ctx context.Context, virtPath string) ([]string, erro
 		virtPath += "/"
 	}
 
-	// we will replace the root directory prefix before returning blob names
-	blobPrefix := d.blobName("")
-
-	// This is to cover for the cases when the rootDirectory of the driver is either "" or "/".
-	// In those cases, there is no root prefix to replace and we must actually add a "/" to all
-	// results in order to keep them as valid paths as recognized by storagedriver.PathRegexp
-	prefix := ""
-	if blobPrefix == "" {
-		prefix = "/"
-	}
-
 	out := []string{}
-
 	listPrefix := d.blobName(virtPath)
+
 	pager := d.client.NewListBlobsFlatPager(&container.ListBlobsFlatOptions{
 		Prefix: &listPrefix,
 	})
@@ -431,7 +420,14 @@ func (d *driver) listBlobs(ctx context.Context, virtPath string) ([]string, erro
 				return nil, fmt.Errorf("required blob property Name is missing while listing blobs under: %s", listPrefix)
 			}
 			name := *blob.Name
-			out = append(out, strings.Replace(name, blobPrefix, prefix, 1))
+
+			// This is to cover for the cases when the rootDirectory of the driver is either "" or "/".
+			// In those cases, there is no root prefix to replace and we must actually add a "/" to all
+			// results in order to keep them as valid paths as recognized by storagedriver.PathRegexp
+			if !strings.HasPrefix(name, "/") { // add leading '/'
+				name = "/" + name
+			}
+			out = append(out, name)
 		}
 	}
 
@@ -446,7 +442,9 @@ func (d *driver) blobName(path string) string {
 		return path
 	}
 
-	return strings.TrimLeft(strings.TrimRight(d.rootDirectory, "/")+path, "/")
+	trimmedRoot := strings.TrimRight(d.rootDirectory, "/")
+	trimmedPath := strings.TrimLeft(path, "/")
+	return trimmedRoot + "/" + trimmedPath
 }
 
 func is404(err error) bool {