The import VM tasks step is shown as ConvertingInstance while its still exporting from vcenter

### problem

The import VM tasks step is shown as ConvertingInstance while its still exporting from vcenter. It needs to show in UI,API the correct step i.e exporting the instance/OVF.

### versions

4.22.0

### The steps to reproduce the bug

1. Import VM from external vCenter
2. Compare the import vm tasks, steps, and actuals in vCenter.

### What to do about it?

Steps should match the actuals.

复现一次从外部 vCenter 执行的导入，并将 UI 和 API 中导入 VM 任务的步骤与实际的 vCenter 操作进行比较。只有当导出阶段显示为正在导出实例/OVF，而不是 ConvertingInstance 时，这项工作才算完成。

由索引模型根据 Issue 内容生成。