GroupsIT: Clean up helper methods

When merging acceptance tests together, all helper methods were
copied wholesale. Eliminate some of the redundancy and use consistent
naming.

There is a slight behavior change in some cases to use the
administrators group as the group owner by default, which is to make
it easier to edit the group from acceptance tests. This does mean that
some asserts needed to be changed, however.

Change-Id: I9b3ea56de0de03d7144a0a56d5fb800f00255544
2 files changed