crio: use system default for storage driver by default (#6637)

After host reboot kubelet and crio goes into a loop and no container is started.

storage_driver in crio.conf overrides system defaults in etc/containers/storage.conf

/etc/containers/storage.conf is installed by package containers-common dependency
installed from cri-o (centos7) and contains "overlay".

Hosts already configured with overlay2 should be reconfigured and the
/var/lib/containers content removed.