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/cmd/cleanup_service.py b/tempest/cmd/cleanup_service.py
index a0bbb70..80f2e22 100644
--- a/tempest/cmd/cleanup_service.py
+++ b/tempest/cmd/cleanup_service.py
@@ -271,7 +271,7 @@
 
     def list(self):
         client = self.client
-        _, secgrps = client.list_security_groups()
+        secgrps = client.list_security_groups()
         secgrp_del = [grp for grp in secgrps if grp['name'] != 'default']
         LOG.debug("List count, %s Security Groups" % len(secgrp_del))
         return secgrp_del