Change security-group clients to return one value and update tests

Partially implements: blueprint clients-return-one-value

Change-Id: Ie49263da72f7f1379320833c3d8ec82cbb61282f
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index 5b092c3..0fcc75b 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -236,7 +236,7 @@
     def _create_loginable_secgroup_rule(self, secgroup_id=None):
         _client = self.security_groups_client
         if secgroup_id is None:
-            _, sgs = _client.list_security_groups()
+            sgs = _client.list_security_groups()
             for sg in sgs:
                 if sg['name'] == 'default':
                     secgroup_id = sg['id']
@@ -263,8 +263,8 @@
         ]
         rules = list()
         for ruleset in rulesets:
-            _, sg_rule = _client.create_security_group_rule(secgroup_id,
-                                                            **ruleset)
+            sg_rule = _client.create_security_group_rule(secgroup_id,
+                                                         **ruleset)
             self.addCleanup(self.delete_wrapper,
                             _client.delete_security_group_rule,
                             sg_rule['id'])
@@ -275,7 +275,7 @@
         # Create security group
         sg_name = data_utils.rand_name(self.__class__.__name__)
         sg_desc = sg_name + " description"
-        _, secgroup = self.security_groups_client.create_security_group(
+        secgroup = self.security_groups_client.create_security_group(
             sg_name, sg_desc)
         self.assertEqual(secgroup['name'], sg_name)
         self.assertEqual(secgroup['description'], sg_desc)