remove tenant-id from uri

Barbican server will be dropping project-id (a.k.a tenant-id)
from its resource API (https://review.openstack.org/#/c/105562/).
Once that happens, the client will be broken. This commit
fixes that by removing all references of tenant-id from the
secret/order resource URIs. Also, for the unauthenticated use
case, the tenant-id is now passed to the server in the request
header as X-Project-Id

Patch Set 7:
  Rebased and fixed merge issue

Change-Id: I9961e13194485b7945060b18130b4b5265022367
Implements: https://blueprints.launchpad.net/barbican/+spec/api-remove-uri-tenant-id
CR: #1353101
Merge "remove tenant-id from uri"