storage: switch default driver to file
storage: switch default driver to file

At least this one will work by default.

Change-Id: Ie897c7ffd8a64f055d69176d5cc319593a949555

idegtiarov/gnocchi-rep,gnocchixyz/gnocchi,leandroreox/gnocchi,gnocchixyz/gnocchi,idegtiarov/gnocchi-rep,sileht/gnocchi,sileht/gnocchi,leandroreox/gnocchi,idegtiarov/gnocchi-rep