Update a test to work with Quantum SecGroup

Nova-Network and Quantum return different error code to an
non existent security group

Fix Bug #1183347

Change-Id: Iae2d86938b5c3df0af99e760ac7933bcdd8f9007
diff --git a/tempest/api/compute/servers/test_servers_negative.py b/tempest/api/compute/servers/test_servers_negative.py
index b369179..25a7522 100644
--- a/tempest/api/compute/servers/test_servers_negative.py
+++ b/tempest/api/compute/servers/test_servers_negative.py
@@ -236,7 +236,11 @@
         # Create a server with a nonexistent security group
 
         security_groups = [{'name': 'does_not_exist'}]
-        self.assertRaises(exceptions.BadRequest,
+        if self.config.network.quantum_available:
+            expected_exception = exceptions.NotFound
+        else:
+            expected_exception = exceptions.BadRequest
+        self.assertRaises(expected_exception,
                           self.create_server,
                           security_groups=security_groups)