Retrying host maintenance falsely marks already-migrated VMs as stopped

CLOUDSTACK VERSION
4.22.1.1, KVM hypervisor

SUMMARY
Putting a host into maintenance moves its VMs off one at a time, which
can take a while. Requesting maintenance again on the same host before
the first request finishes causes it to retry moving every VM still
listed against that host, including ones already moved. That retry
fails as expected, but for some VMs it confuses CloudStack into
thinking the VM was powered off, and it gets marked stopped even though
it was never touched and kept running the whole time.

EXPECTED
Requesting maintenance again should not retry VMs already moved.

ACTUAL
Some already-moved VMs get falsely marked stopped.

NOTE
The false "stopped" status seems to come from CloudStack losing track
of which VMs are on which host. That could plausibly happen from causes
other than this one, but we only have evidence of it via this scenario.

首先，在 CloudStack 4.22.1.1 中的 KVM 主機上重現重複的維護請求，然後追蹤主機維護 VM 的遷移流程，以及主機的 VM 清單如何更新。完成的標準是：第二次請求會略過已經遷移的 VM，且這些 VM 會繼續執行，而不是被標記為已停止。

由索引模型根據 Issue 內容生成。