gluon-mesh-batman-adv: fix network.mesh_inferfaces announce field with new netifd

package/gluon-mesh-batman-adv/files/lib/gluon/announce/nodeinfo.d/network/mesh_interfaces

-require 'ubus'
-
-local conn = ubus.connect()
 local list = util.exec('batctl if')
 
 local interfaces = {}
 for _, line in ipairs(util.split(list)) do
-	local ifname = line:match('^(.-):')
-	if ifname ~= nil then
-		local status = conn:call("network.device", "status", { name = ifname })
-		table.insert(interfaces, status['macaddr'])
-	end
+  local ifname = line:match('^(.-):')
+  if ifname ~= nil then
+    pcall(
+      function()
+	table.insert(interfaces, util.trim(fs.readfile('/sys/class/net/' .. ifname .. '/address')))
+      end
+    )
+  end
 end
 
 return interfaces