gluon-mesh-batman-adv-core: always set hop penalty to 15

15 is the default in batman-adv-legacy, the new default 30 in newer batman-adv
versions is too high in larger networks.

package/gluon-mesh-batman-adv-core/files/lib/gluon/upgrade/310-gluon-mesh-batman-adv-core-mesh

@@ -11,6 +11,7 @@ uci:section('batman-adv', 'mesh', 'bat0',
 	    {
 		    orig_interval = 5000,
 		    gw_mode = 'client',
+		    hop_penalty = 15,
 		    multicast_mode = 0,
 	    }
 )