Interpret DHCPv6 DUID-UUID type

Interpret DHCPv6 DUID-UUID type

Dissect DUID type 4 as DUID-UUID type specified in RFC 6355.

Note: The previously implemented interpretation of DUID type 4 as
      link-layer address (old) was according to DHCPv6 draft version 24
      which was removed again in revision 26 of the document, see [1][2].

[1] - http://www.ietf.org/rfcdiff?url1=draft-ietf-dhc-dhcpv6-23&url2=draft-ietf-dhc-dhcpv6-24
[2] - http://www.ietf.org/rfcdiff?url1=draft-ietf-dhc-dhcpv6-25&url2=draft-ietf-dhc-dhcpv6-26

Change-Id: Iaa2c083b7b1fd9f5fed959d436cbe0df71b98c0b
Reviewed-on: https://code.wireshark.org/review/11030
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>