Move seed normalization test from "single" to "sharded" directory.

The Server Discovery And Monitoring Spec does not allow multiple seeds for
TopologyType "Single". Moving this test has no functional impact but makes
more sense in the "sharded" directory, since it tests a client connecting with
multiple seeds and no replica set name.
Merge pull request #10 from ajdavis/move-seed-normalization-test

Move seed normalization test from "single" to "sharded" directory.