Space Accounting may encounter erroneous state on data migration

[jwuensche]

This has been observed sporadically when many nodes are migrated. In observed cases, the free storage counter overstepped the total counter which should not happen at all, but some construction may lever this behavior. Needs further investigation.

[jwuensche]

Recovered from observed case:

[src/scientific_evaluation.rs:50] client.database.read().free_space_tier() = [
    StorageInfo {
        free: Block(
            1112623,
        ),
        total: Block(
            4194304,
        ),
    },
    StorageInfo {
        free: Block(
            5480030,
        ),
        total: Block(
            5242880,
        ),
    },
    StorageInfo {
        free: Block(
            0,
        ),
        total: Block(
            0,
        ),
    },
    StorageInfo {
        free: Block(
            0,
        ),
        total: Block(
            0,
        ),
    },
]

[jwuensche]

This has been fixed with the rework of the migration policy.