cleanup: no magic number for RWX permissions
cleanup: no magic number for RWX permissions

golang-ci complains that 0777 is a magic number, so make it a constant
with a clear description.

Signed-off-by: Niels de Vos <7bda0c0ee7f47171cc808e9e60292cbc5d8140dd@redhat.com>

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