gluon-mesh-batman-adv: don't parse ip output for nodeinfo

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

@@ -1,8 +1,12 @@
-local ip = util.exec('ip -o -6 addr show dev br-client')
+local ip = require 'luci.ip'
 
 local addresses = {}
-for _, line in ipairs(util.split(ip)) do
-	table.insert(addresses, line:match('inet6 ([%x:]+)/'))
+
+for line in io.lines('/proc/net/if_inet6') do
+  local matches = { line:match('^' .. string.rep('(%x%x%x%x)', 8) .. string.rep(' %x%x', 4) .. '%s+([^%s]+)$') }
+  if matches[9] == 'br-client' then
+    table.insert(addresses, ip.IPv6(string.format('%s:%s:%s:%s:%s:%s:%s:%s', unpack(matches))):string():lower())
+  end
 end
 
 return addresses