Generic volume groups support was added to Cinder in the
Newton release. Group types APIs were added as part of that.
https://blueprints.launchpad.net/cinder/+spec/generic-volume-group
This patch adds the tempest tests for group types APIs
in Cinder. It tests the following APIs:
* create group type
* delete group type
* show group type
* list group types
Change-Id: Ic409db6f1258befc6f1772ea19e7e634170269f8