dpif-netlink-rtnl: Fix netdev leak in out-of-tree tunnels probe.

Caught by code review, calling netdev_open works in pair of netdev_close
when no reference to a netdev must be kept.

Fixes: 921c370 ("dpif-netlink: Probe for out-of-tree tunnels, decides used interface")
Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Eric Garver <eric@garver.life>
Signed-off-by: Simon Horman <horms@ovn.org>

lib/dpif-netlink-rtnl.c

@@ -561,6 +561,7 @@ dpif_netlink_rtnl_probe_oot_tunnels(void)
 
         tnl_cfg = netdev_get_tunnel_config(netdev);
         if (!tnl_cfg) {
+            netdev_close(netdev);
             return true;
         }