Send IPv6 metadata traffic (dst=fe80::a9fe:a9fe) to the metadata-agent.
When running on IPv6 enabled system bind haproxy (i.e. the
metadata-proxy) to 169.254.169.254 and to fe80::a9fe:a9fe also.
We do not introduce new config options. The usual config options
(enable_isolated_metadata, force_metadata, enable_metadata_proxy)
now control the metadata service over both IPv4 and IPv6.
This change series only affects the guests' access to the metadata
service (over tenant networks). They change nothing about how the
metadata-agent talks to Nova's metadata service.
Metadata access over IPv6 is supposed to work both on dual-stack and
v6-only networks.
In order to enable the metadata service on pre-existing isolated
networks during an upgrade, this change makes each dhcp-agent restart
trigger a quick restart of dhcp-agent-controlled metadata-proxies,
so they can pick up their new config making them also bind to
fe80::a9fe:a9fe.
Change-Id: If35f00d1fc9e4ab7e232660362410ce7320c45ba
Partial-Bug: #1460177
a0b18d553d