Switch to the default os-refresh-config base dir

The default os-refresh-config base dir changed over 6 months
ago in I98e93d91685ae25ae74a5470483a1cc8b97da4e5.
Using the deprecated default may cause problems in the future,
instead query os-refresh-config for the default directory.

Change-Id: Ia5b8fceb83ebd32d9a537d793a80cd2b8341c8ec
Merge "Switch to the default os-refresh-config base dir"