Fix IBM copyright strings

Update IBM copyright strings to one consistant format

Change-Id: I56bd87dd84a78cc5336d31c3af701941c48e1539
diff --git a/tempest/services/compute/xml/limits_client.py b/tempest/services/compute/xml/limits_client.py
index d233bba..704de52 100644
--- a/tempest/services/compute/xml/limits_client.py
+++ b/tempest/services/compute/xml/limits_client.py
@@ -1,6 +1,6 @@
 # vim: tabstop=4 shiftwidth=4 softtabstop=4
 #
-# Copyright 2012 IBM
+# Copyright 2012 IBM Corp.
 # All Rights Reserved.
 #
 #    Licensed under the Apache License, Version 2.0 (the "License"); you may