Inspector-client is a bit lacking behind other clients, as it does not
have Adapter-based SessionClient and thus does not support all
adapter-related options.
That's why we construct a session and an adapter from config section,
use adapter to resolve inspector API from service catalog
(or return the fixed endpoint_override one)
and then pass the session and inspector API endpoint to client.
This patch also deprecates `[inspector]service_url` in favor of
`[inspector]endpoint_override`.
As a side-effect, addressig inspector service now supports both regions
and interfaces to specify entry in service catalog.
Also, inspectorclient calls are now being made with the user token
(wrapped with a service token) when there is a token in the task's
request context.
Change-Id: I21836e712fa9764468ac2654525554b5b4f03741
Partial-Bug: #1699547