* Fixes the IPv6 job by utilizing HOST_IPV6 instead of
SERVICE_IPV6, as Devstack now automatically wraps
SERVICE_IPV6 with brackets as if it is for a URL.
* Locks ipv6 job to bios mode. Ubuntu Focal OVMF/EDK2 does not
support IPv6 PXE boot by default.
* Split from Devstack in terms of IP usage, since full explicit
V6 usage is not a thing anymore. 4+6 is the default in devstack
and regardless of what we set on the job we see both now used.
So we delineate apart our usage for our own sanity.
* Reduce VM Interface count for IPv6 in an attempt to eliminate
in-kernel routing confusion by two interfaces on the same physical
network.
* Set IPv6 mode to dhcpv6-stateless due to fun issues in dhcp clients.
When we move to UEFI, this will need to be changed to stateful as
stateless is not supported in general by OVMF/E2DK.
Once the job has run in normal non-voting for a while, and we
ensure that it seems to be stable, we can make it voting again.
Change-Id: Ia833bfb64c6c3cc8e48cbe34ed200536652a8adf
a9f4acfdb0