Group operations: add QA tests for add/remove/rename

This is a single function that tests all of of the following:

  - creating groups
  - creating groups that exist fails
  - renaming an empty group
  - renaming a group with nodes
  - renaming to a name that already exists fails
  - removing an empty group works
  - removing a group with nodes fails

The "default" group is only used for the "rename group with nodes"
test.

Signed-off-by: Adeodato Simo <dato@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>