Race condition between polling and watcher

[mizdebsk]

Today I've observed the following sequence of events:

• Feb 05 15:50:08 koschei-polling: Polling latest real builds...
• Feb 05 15:50:45 koji: rubygem-thor-0.20.3-1.fc30 tagged into f30 by autopen
• Feb 05 15:50:45 koschei-watcher: Registering real build rubygem-thor-0.20.3-1.fc30 for collection Fedora rawhide (task_id 32554657)
• Feb 05 15:51:20 koschei-polling: Build(id=5990932, package=rubygem-thor, collection=f30, state=complete, task_id=32554657) is no longer tagged

Polling started a long Koji query to get latest packages in a tag. In meantime, a build was tagged in Koji and registered in DB by watcher. When the query completed, it didn't include newly tagged build, so the build was marked as untagged.