Delete import-queue entries for obsolete distroseries

[Jeroen T. Vermeulen]

Arne points out that Dapper and Gutsy right now make up about ⅓ of the import queue—and of those entries, the only ones that will ever be needed again are for Dapper Server.

So we could clean up the queue considerably by deleting entries for obsolete series in batches. For instance, we could run this once an hour:

DELETE FROM TranslationImportQueueEntry
WHERE id IN (
    SELECT Entry.id
    FROM TranslationImportQueueEntry Entry
    JOIN DistroSeries ON DistroSeries.id = Entry.distroseries
    WHERE DistroSeries.releasestatus = 6
    LIMIT 100
)

Takes almost no time to execute, doesn't stress replication much, but would clear out the Gutsy queue within two weeks.