PR #1736 made the kubelet path configurable. It also introduced a change in
the path to the CSI socket. By default the path is now
`/var/lib/kubelet/cephfs.csi.ceph.com/csi.sock` instead of
`/var/lib/kubelet/plugins/cephfs.csi.ceph.com/csi.sock`. This PR
restores the old default.
Signed-off-by: Matthias Neugebauer <matthias.neugebauer@uni-muenster.de>