Single AVP should not be padded with zeros as padding is only
used to separate AVPs in a sequence.
RFC 5281 Section 10.2. AVP Sequences
Data encapsulated within the TLS record layer must consist entirely
of a sequence of zero or more AVPs. Each AVP must begin on a four-
octet boundary relative to the first AVP in the sequence. If an AVP
is not a multiple of four octets, it must be padded with zeros to the
next four-octet boundary.
Note that the AVP Length does not include the padding.