rgw: Object::Read::read() returns total bytes read

Signed-off-by: Yehuda Sadeh <yehuda@redhat.com>
rgw: fix (squash)
rgw: Object::Read operations should use state->obj

and not the provided obj, as it might have been an olh, therefore we
have prepare() that sets the state.obj as the effective object.

Signed-off-by: Yehuda Sadeh <yehuda@redhat.com>
rgw: reduce use of Object::get_obj()

We should avoid using this one, as it's not going to point at the object
instance in case it's an olh. Only kept the use in
Object::Delete, as we make explicit checks before using it.

Signed-off-by: Yehuda Sadeh <yehuda@redhat.com>
rgw: parse copy location version id

Signed-off-by: Yehuda Sadeh <yehuda@redhat.com>