Comment 6 for bug 1639930

The test cases described in bug 1621507 cover the code path that this change
was done to fix. Additionally, unit tests (which run during build) were added
to verify the failing code path.

Specifically, this bug would be seen when the system was booted with
both ip= and ip6= on the kernel command line.
 [+]/[+] MAAS booting IPv4 on dual-stack network (with and without dhcp6)
 [+]/[+] MAAS booting IPv6 on dual-stack network (with and without dhcp4)

As a result of the tests mentioned above having been done, I am marking
this bug as verification-done.