maintenance/commandLine.inc loads DefaultSettings, LocalSettings and then runs Setup.php
As Setup.php assigns variables based on the cache config, bootstrap.php was late on reseting them, as some objects were already created.
So we could end up with a SqlBagOStuff created there, which when later accessed (such as trying to invalidate the cache for a user) would
-as any non-sqlite SqlBagOStuff- open a new db connection. Which is precisely what we shall not be done when dealing with temporary tables
(and would indeed fail miserably due to not finding unittest_objectcache table).
In summary, reenabling temporary tables disabled in r79411.