Comment 9 for bug 1324311

Got this suggestions from Evgeny as a workaround:

```
you could first delete questions that are marked as deleted,
then run "python manage.py delete_unused_tags"

To delete threads:

1) back up the database

2) do the following:

# python manage.py shell
>>> from askbot.models import Thread
>>> Thread.objects.filter(deleted=True).delete()
>>> exit()

# python manage.py delete_unused_tags

```