[disk]linux: fix test

disk/disk_test.go

@@ -96,7 +96,7 @@ func TestDiskIOCountersStat_String(t *testing.T) {
 		WriteBytes:   400,
 		SerialNumber: "SERIAL",
 	}
-	e := `{"readCount":100,"mergedReadCount":0,"writeCount":200,"mergedWriteCount":0,"readBytes":300,"writeBytes":400,"readTime":0,"writeTime":0,"iopsInProgress":0,"ioTime":0,"weightedIO":0,"name":"sd01","serialNumber":"SERIAL"}`
+	e := `{"readCount":100,"mergedReadCount":0,"writeCount":200,"mergedWriteCount":0,"readBytes":300,"writeBytes":400,"readTime":0,"writeTime":0,"iopsInProgress":0,"ioTime":0,"weightedIO":0,"name":"sd01","serialNumber":"SERIAL","label":""}`
 	if e != fmt.Sprintf("%v", v) {
 		t.Errorf("DiskUsageStat string is invalid: %v", v)
 	}