minor changes for address conversion


git-svn-id: https://gnunet.org/svn/gnunet@32873 140774ce-b5e7-0310-ab8b-a85725594a96
- check handles on send_echo, fix #3349

git-svn-id: https://gnunet.org/svn/gnunet@32874 140774ce-b5e7-0310-ab8b-a85725594a96
- log checksum error (for #3333)

git-svn-id: https://gnunet.org/svn/gnunet@32875 140774ce-b5e7-0310-ab8b-a85725594a96