Add tests for update group types for volume module

This PS adds a test for update_group_types for the corresponding
Cinder API that was recently added to Tempest [0] and whose policy
is [1].

This PS also rearranges some tests in the related class so that
the tests are bunched together by policy name.

[0] https://github.com/openstack/tempest/blob/1879cc7aa733f38bc5eba1d126bd320dfeaa1a90/tempest/lib/services/volume/v3/group_types_client.py#L79
[1] https://github.com/openstack/cinder/blob/280e59c5b6c953228dcba52b21587b82f7f5f93b/cinder/policies/group_types.py#L38

Change-Id: Ie9bf27c9e9c392ebb2011800e5ce5c1450c3df75
1 file changed