The client tries to authenticate even if a token is already provided to it

The client tries to authenticate even if a session or auth is already provided to it. This is problematic because it may not be possible to re-authenticate and wastes resources. The client should accept the token it is passed and as long as the connection parameters are sufficient, it should simply connect to the server and leave the token verification to the server side.

Note: other OS service clients do not re-authenticate.

Reproduce:

v2.client.Client(mistral_url=SOMEURL, session=session, auth=Token(...))