To avoid switching existing deployments from devicemapper to overlay2,
we check the existing storage driver configuration directly with the
Docker daemon, or if unreachable by reading the /etc/docker/daemon.json
configuration file.
Co-Authored-By: Pierre Riteau <pierre@stackhpc.com>
Story: 2005667
Task: 30972
Change-Id: Iaf2ee8c9f302f4684ae039bb00b2e2e5969cf1fc