Replace auth fragements with identity_uri

The need for individual auth_host, auth_port etc variables for
auth_token middleware made some sense when we were using httplib however
as we have long moved on to requests they are no longer required and are
a pain for configuration.

DocImpact: auth_schema, auth_host, auth_port, auth_admin_prefix are all
deprecated in favour of specifying the full url in the identity_uri
property.

Blueprint: identity-uri
Change-Id: I1f8f5064ea8028af60f167df9b97e215cdadba44
Rename request_uri to identity_uri

This makes it more consistent with the CONF options.

Blueprint: identity-uri
Change-Id: If4e32d232413e539b4c29035b253e9368b3fbd06
Merge "Replace auth fragements with identity_uri"
Merge "Rename request_uri to identity_uri"