Refactor Managers to a common base class

Multiversion auth part3

Refactor client managers to inherit from a common manager.Manager
class. Moves scenario base manager to clients.py.

Partially implements: bp multi-keystone-api-version-tests

Change-Id: Iddacbaa4593b7cb4d32538a5cade814751c180e0
diff --git a/tempest/scenario/test_security_groups_basic_ops.py b/tempest/scenario/test_security_groups_basic_ops.py
index eabc734..d4de109 100644
--- a/tempest/scenario/test_security_groups_basic_ops.py
+++ b/tempest/scenario/test_security_groups_basic_ops.py
@@ -13,13 +13,13 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from tempest import clients
 from tempest.common import debug
 from tempest.common.utils import data_utils
 from tempest import config
 from tempest import exceptions
 from tempest.openstack.common import log as logging
 from tempest.scenario import manager
-from tempest.scenario.manager import OfficialClientManager
 from tempest.test import attr
 from tempest.test import call_until_true
 from tempest.test import services
@@ -102,7 +102,7 @@
         """
 
         def __init__(self, tenant_id, tenant_user, tenant_pass, tenant_name):
-            self.manager = OfficialClientManager(
+            self.manager = clients.OfficialClientManager(
                 tenant_user,
                 tenant_pass,
                 tenant_name