Fix volume group test
Fix volume group test

This patch mainly aims to fix GroupsTest.test_group_create_show_list_delete.
The method to verify 'list' API is not quite right, it should check whether
all the groups are present and unique in the result of list_groups.

Change-Id: I882cdbc38efc6f876757db3d27344c68f4e54881

masayukig/tempest,openstack/tempest,masayukig/tempest,cisco-openstack/tempest,Juniper/tempest,Juniper/tempest,openstack/tempest,cisco-openstack/tempest