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.
It's probably sufficient to just check the authURI since if these other properties are missing it will fail anyway.  Trying to use a non-authed connection as a failure case would fail anyway if auth was enabled.