While listmanager called |kickoffUpdate|, it used to call |GetTables| to
retrieve update information and used the information to distinguish if
a table is a "existing" table or not.
In Bug 1045163, the "existing table" logic was removed, which also means we
don't need to call |GetTabkes| anymore. This patch removes calling
Classifier::TableRequest to reduce unnecessary disk IO during startup.
Differential Revision: https://phabricator.services.mozilla.com/D37037
270a61b3ea