Since inception RGWReaddirRequest has sent all leaf objects first
(in lexical order), then common_prefixes (in lexical order). In
hindsight, an overall listing could trivially be returned out of
lexical order, which can cause continued listing of large, mixed
directories to fail.
RCA by Dan Gryniewicz.
Fixes: https://tracker.ceph.com/issues/48410 Signed-off-by: Matt Benjamin <mbenjamin@redhat.com>