Add descriptions for auth_strategy choices
Add descriptions for auth_strategy choices

Starting with oslo.config 5.2.0, provided config choices can
include a description in the generated config sample if one
is provided. Without a description, it states "No description
provided". This adds descriptions to the auth_strategy config
option choices for better clarity.

Change-Id: I39bdefbef1200aaeb029d7aa40389b02b4cdce72

mahak/cinder,openstack/cinder,openstack/cinder,mahak/cinder