nbd/server: Allow LIST_META_CONTEXT without STRUCTURED_REPLY
The NBD protocol just relaxed the requirements on
NBD_OPT_LIST_META_CONTEXT:
https://github.com/NetworkBlockDevice/nbd/commit/
13a4e33a87
Since listing is not stateful (unlike SET_META_CONTEXT), we don't care
if a client asks for meta contexts without first requesting structured
replies. Well-behaved clients will still ask for structured reply
first (if for no other reason than for back-compat to older servers),
but that's no reason to avoid this change.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <
20210907173505.
1499709-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>