Merge DefaultGroupsIT into ListGroupsIT

Based on review traffic[1] I don't think anybody was recommending
this test as an example integration test, as the class javadoc
claimed. It does have a marginally useful assertion, but we can just
roll that into ListGroupsIT to avoid the extra test setup.

[1] http://gerrit-review.googlesource.com/#/q/DefaultGroupsIT

Change-Id: Iaddeefb6dc21c1548dfee237c4f76a22c23dccc6
2 files changed