dec-dnart: use pinfo-scoped memory for addresses

They may be accessed during the print phase, at which point packet-scope memory
has already been freed.

Bug: 10724
Change-Id: Ifcf5fc0c0857614edf85349b12dfe605abf6fef7
Reviewed-on: https://code.wireshark.org/review/5499
Reviewed-by: Michael Mann <mmann78@netscape.net>