Remove deprecated auth_token middleware

The actual code for auth_token has been moved python-keystoneclient
since Grizzly, and keep it in keystone for backward compatibility
over Havana Release. So now we can safely remove it in Icehouse.

bp icehouse-deprecated-removed

Change-Id: I6bfc92c2cb9d836bdc7130910a679a8b660096e9
Merge "Remove deprecated auth_token middleware"