[V3] Make groups_client use **kwargs

As we discussed on
http://lists.openstack.org/pipermail/openstack-dev/2015-July/068864.html
All http POST/PUT methods need to contain **kwargs as their arguments.
This patch makes groups_client use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: I558453a64247835b117f4612064a381ad84f3513
diff --git a/tempest/api/identity/admin/v3/test_roles.py b/tempest/api/identity/admin/v3/test_roles.py
index 524340c..eb6b7ee 100644
--- a/tempest/api/identity/admin/v3/test_roles.py
+++ b/tempest/api/identity/admin/v3/test_roles.py
@@ -40,7 +40,7 @@
             description=data_utils.rand_name('project-desc'),
             domain_id=cls.domain['id'])['project']
         cls.group_body = cls.groups_client.create_group(
-            data_utils.rand_name('Group'), project_id=cls.project['id'],
+            name=data_utils.rand_name('Group'), project_id=cls.project['id'],
             domain_id=cls.domain['id'])['group']
         cls.user_body = cls.client.create_user(
             u_name, description=u_desc, password=cls.u_password,