cephfs: set pool layout of the FS subvolumes
cephfs: set pool layout of the FS subvolumes

... instead of that of the `csi` subvolume group. The pool layout
specified via storage class's `pool` setting is a subvolume property
and not a subvolume group property. The `csi` subvolume group
may have subvolumes of different storage classes with different
pool layouts.

Fixes: #499
Signed-off-by: Ramana Raja <1313a362c0d8582c598799adfe7f06a7b14e2f97@redhat.com>

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