cleanup: return InvalidPoolID on error in GetPoolID()
cleanup: return InvalidPoolID on error in GetPoolID()

InvalidPoolID has recently been added, and can be used in other location
too. As GetPoolID is updated with this patch set, return InvalidPoolID
on errors too.

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

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