Currently we have very similar service user authentication code
partially duplicated in the following areas:
* nova/image/glance.py
* nova/network/neutron.py
* nova/volume/cinder.py
* nova/api/metadata/vendordata_dynamic.py
This attempts to commonize and reuse code as much as possible from the
service_auth module in preparation of vTPM live migration patches.
Change-Id: I3a5c00e434eb6ce7956a717dffd11f38f19c5f7d
Signed-off-by: melanie witt <melwittt@gmail.com>