This patch adds support to retrieve IPv6 address.
A new field ``ipv6_address`` is added to NetworkInterface
and store the assigned IPv6 address (if any).
Co-Authored-By: Kaifeng Wang <kaifeng.w@gmail.com>
Change-Id: Ia527a5aa48e3daf66d2be190e43935b38b3bd6f9
Closes-Bug: #1744064
Story: #1744064
Task: #11604