Replace OpenStack LLC with OpenStack Foundation

Some files still use trademark OpenStack LLC in header, which
should be changed to OpenStack Foundation.

NOTE: tools/install_venv.py is not synced from oslo-incubator, so
it is modified too.

Change-Id: I0084684ff5225076291fea857eb010d638291bd0
Fixes-Bug: #1214176
diff --git a/tempest/common/rest_client.py b/tempest/common/rest_client.py
index d0d5e84..a867a12 100644
--- a/tempest/common/rest_client.py
+++ b/tempest/common/rest_client.py
@@ -1,6 +1,6 @@
 # vim: tabstop=4 shiftwidth=4 softtabstop=4
 
-# Copyright 2012 OpenStack, LLC
+# Copyright 2012 OpenStack Foundation
 # Copyright 2013 IBM Corp.
 # All Rights Reserved.
 #