rbd: remove unused rbdVolume.open()
rbd: remove unused rbdVolume.open()

rbdVolume.open() was split from commit 5dd34732e1e while moving part of
the functionality to util.ClusterConnection. It seems that .open() is
not used anywhere at the moment, so drop it until follow-up patches
require it again.

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

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