cleanup: replace parentName to snapParentName in checkReservation
cleanup: replace parentName to snapParentName in checkReservation

at present, eventhough the checkReservation works for both volume
and snapshot, the arg parentName make sense only for snapshot cases
renaming that arg to more approprite

Signed-off-by: Humble Chirammal <dc8ba7e82a7df22725dedec9b10c7aaab9ec713f@redhat.com>

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