Migration leave host in incorrect state after completion

When migrating a VM from an host to another using `migrate_send` API, the migrate task is never cleaned from the receiving host's `current-operations` even though the migration is finished.
Only a toolstack restart allows to remove the ghost operation.

For that issue to happen, you need to make sure that the storage is also migrating while migrating the VM (no shared SR).
Here's how the receiving host current-operations is left:
current-operations (SRO): VM.migrate