Remove spec for fileset from dataset (See #11054)

All chgrp and delete activities need now be performed
within a DoAll due to the ordering of the Fileset
element. It's not currently possible to support the
DoAll and non-DoAll case.
Do not re-use the Deletion object in DeleteI

Each ome.services.delete.Deltion instance (injected
via the RequestObjectFactory) is intended to be used
just once. clone()'ing the DeleteI leads to the
instance being shared between requests.