Add Apache 2.0 license to source file
Add Apache 2.0 license to source file

As per OpenStack licensing guide lines [1]:
[H102 H103] Newly contributed Source Code should be licensed under
the Apache 2.0 license.
[H104] Files with no code shouldn't contain any license header nor
comments, and must be left completely empty.

[1] http://docs.openstack.org/developer/hacking/#openstack-licensing

Change-Id: I15cbb71d028e9297cb49b5aab7d0427f7be36c49

openstack/python-glanceclient,openstack/python-glanceclient