qemu-nbd: document -v behavior in respect to --fork in man

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Eric Blake <eblake@redhat.com>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-ID: <20230906093210.339585-8-den@openvz.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: Wording improvement]
Signed-off-by: Eric Blake <eblake@redhat.com>
1 file changed