Add test coverage for SignalResponder delete

Add coverage for the case where the user has been deleted out of band
and keystoneclient raises a NotFound exception.  Brings coverage of
SignalResponder up to 100%

Change-Id: I29ea94b052f807072d98e05768e6a1973df5d40d
Add policy enforcement to ReST API

Currently the native API lacks support for enforcing policy via
policy.json, as is possible for the aws-compatible APIs.

So modify and rename the tenant_local decorator to also enforce
policy, and add tests to ensure the API controllers are all
using the decorator on their actions

Change-Id: Id80d576d5ff5e546da42dbf08ebd653005af14ff
blueprint: request-scoping-policy
Merge "Add policy enforcement to ReST API"
Merge "Add test coverage for SignalResponder delete"