Fix to exclude downloads of public plans with no user id usually associated with robots

[johnpinto1]

Fix to exclude downloads of public plans with no user id associated with download, as most of these downloads are associated with robots.

Change:

• We exclude the count of downloads in export_plans table for which user_id is nil.

To Test:

• First, get a snapshot of the monthly download for an org. We are interested in recent stats (when robots seem to start downloading public plans), e,g.,

• Now we need to delete the data in the stats table before we regenerate it with:

  DELETE from stats;

• Now run (this could take 15 - 30 min)

  bundle exec rails stat:build

• Now you should be able download the usage monthly stats again for your org and get something with download figures reduced drastically for recent period.