Updated Shard Splitter to be Auth aware

When connecting to a sharded cluster that has authentication enabed, the Sharded mongo splitter fails initialize the Mongo object with an Auth URI. This caused the call to the config database to fail as unauthorized.
Notice how there's no way that getCollectionWithAuth is called in this flow. Maybe I'm missing something, or maybe we have a weird config, but this was breaking for us, and now works.