Update group README file and add tests for executing plugin with
`ipaapi_context` set to `client`.
A new test playbook can be found at:
tests/group/test_group_client_context.yml
The new test file can be executed in a FreeIPA client host that is
not a server. In this case, it should be defined in the `ipaclients`
group, in the inventory file.
Most tests have simply been using the Tests as name, but this there is a
lack of information in automated runs. The name should be similar to the
test file name.
The changed flag returned by ipagroup calls have not been correct. This
change fixes this. Addtitionally new test cases have been added to make
sure that the changed flag is correct.
