nbd/server: fix TRACE in nbd_negotiate_send_rep_len

Fix wrong order of TRACE arguments.
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170707152918.23086-8-vsementsov@virtuozzo.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

nbd/server.c

@@ -139,7 +139,7 @@ static int nbd_negotiate_send_rep_len(QIOChannel *ioc, uint32_t type,
     uint64_t magic;
 
     TRACE("Reply opt=%" PRIx32 " type=%" PRIx32 " len=%" PRIu32,
-          type, opt, len);
+          opt, type, len);
 
     magic = cpu_to_be64(NBD_REP_MAGIC);
     if (nbd_write(ioc, &magic, sizeof(magic), errp) < 0) {