The function dec_addr_tlv() takes an encoded FQDN or IPv4 address and
fromats it into a human readable string that contains the human readable
form and the encoded hex form. Unfortunately this limits the usecase of
dec_addr_tlv. Lets split the string generation into a separate function
so that we can use dec_addr_tlv universally
Change-Id: Id017b0786089adac4d6c5be688742eaa9699e529
Related: OS#4963