remove project-id from resource URIs

All Barbican resources have a project-id in their URI. This helps to
correlate the resource with the specified project when no external
authentication mechanism is used. However, most Barbican deployments
would use Keystone to authenticate the API requests. With Keystone,
the project-id information is already obtained when the X-Auth-Token
header from the request is validated. This makes the project-id in the
URI redundant. This commit removes project-id from the URI.

Tests have been updated as well to not expect project-id in the URI.

Patch 3:
  removed unauthenticated-context from admin pipeline to fix
  tempest failure. version api doesn't need auth context now
Patch 4:
  refactored based on review comments
  removed the Noop policy enforcer class
Patch 5:
  rebased and fixed failing tests
  fixed issue in parsing performance_uri
Patch 6:
  updated functional tests to remove project-id from uri
  removed rbac check for versions controller
  expecting X-Project-ID to be present in request for all requests
  this needs to be fixed in the next pass when the admin paste
  pipeline is updated
Patch 7:
  fixed failing functional test
  refactoring based on review comments
Patch 8:
  rebased and fixed failing unit tests
Patch 9:
  fixed merge issue by removing keystone_id from few more lines
  and files
Patch 10:
  fixed failing functional tests (consumers)

Spec: https://review.openstack.org/#/c/100386
Client CR: https://review.openstack.org/#/c/112149
Change-Id: If54911718188eb26b7380331d0b61d70206522a5
Blueprint: https://blueprints.launchpad.net/barbican/+spec/api-remove-uri-tenant-id
Refactor secret_store for consistency

Mostly re-arranged the code a bit, so that for...else... Statements are
used in a more consistent way. On the other, the exception
SecretStorePluginsNotConfigured was introduced to more properly reflect
the occations where the plugins have not been configured correctly.

Change-Id: I84693a65c6e6b44cb81973590ff8c62f28c0b068
Merge "remove project-id from resource URIs"
Merge "Refactor secret_store for consistency"