Validate token calls return 404 on invalid tokens

Invalid X-Subject-Token was resulting in HTTP 401 rather than 404
This is causing the auth_token middleware to re-authenticate
It expects a 404 on an invalid token.

Change-Id: Ieb4cbd4f69b4f3c5944eebc262e694e831d1ca6d
Fixed-Bug: #1221889
Fixed-Bug: #1186059
Merge "Validate token calls return 404 on invalid tokens"