Add security group to large_ops test

There have been some issues with performance around security groups in
the past. Lets make sure they don't exist.

We gate on test_large_ops as part of gate-tempest-devstack-vm-large-ops

Change-Id: Ib655deab9fc12df969b47552d7d8edc999c0d06a
diff --git a/tempest/scenario/test_large_ops.py b/tempest/scenario/test_large_ops.py
index 0bb57ab..22c543b 100644
--- a/tempest/scenario/test_large_ops.py
+++ b/tempest/scenario/test_large_ops.py
@@ -24,7 +24,7 @@
 LOG = logging.getLogger(__name__)
 
 
-class TestLargeOpsScenario(manager.OfficialClientTest):
+class TestLargeOpsScenario(manager.NetworkScenarioTest):
 
     """
     Test large operations.
@@ -85,10 +85,12 @@
         name = rand_name('scenario-server-')
         client = self.compute_client
         flavor_id = self.config.compute.flavor_ref
+        secgroup = self._create_security_group()
         self.servers = client.servers.create(
             name=name, image=self.image,
             flavor=flavor_id,
-            min_count=self.config.scenario.large_ops_number)
+            min_count=self.config.scenario.large_ops_number,
+            security_groups=[secgroup.name])
         # needed because of bug 1199788
         self.servers = [x for x in client.servers.list() if name in x.name]
         for server in self.servers: