language pack export locking DistroSeries table

When the language pack export script is run, it holds open a row exclusive lock in the DistroSeries table, which amongst other things blocks uploads to that distro series from soyuz.

We need to work out why the distro series row is being modified early in the process, and either start a new transaction after the modification is done or ensure the modification is done at the end of the transaction.

There is a chance this behavior is old, and just hasn't been noticed before, or that a change made outside the language pack exporter was the trigger (eg. a new side effect on an operation, or the ORM flushing changes sooner that previously).