The first DHCPv6 related fix was not enough.
In testing, it appears that we were not correctly returning
the proper variables and formatting to enable the machine to
boot via IPv6.
Fixes values, wraps a bare IPv6 address as dicated by RFC standards,
and enhances unit tests.
Change-Id: I9ebfb1ff1ba53dd117988b5e2a7736e20d1041a0