CID 1488362 points out that the second 'rc >= 0' check is now dead
code.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Fixes: 172f5f1a(nbd: remove peppering of nbd_client_connected)
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20220516210519.76135-1-eblake@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy <v.sementsov-og@mail.ru>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>