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 touched, should sync with oslo,
so does trove/openstack/common/*

Change-Id: I7218ae896eb7db681bb224a209df47f203952606
Fixes-Bug: #1214176
Merge "Replace OpenStack LLC with OpenStack Foundation"