Fix Cephfs plugin to return false to ValidateVolumeCapabilities if Block volume is specified
Fix Cephfs plugin to return false to ValidateVolumeCapabilities if Block volume is specified

Cephfs doesn't have a feature to provide Block Volume, therefore it should return false to ValidateVolumeCapabilities if Block Volume is specified.

Fixes #44

ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi