If the dual-stack flag is enabled and the cluster is single stack IPv6,
the allocator logic for service clusterIP does not properly handle rejecting
a request for an IPv4 family. Return a 422 Invalid on the ipFamily field
when the dual stack flag is on (as it would when it hits beta) and the
cluster is configured for single-stack IPv6.
The family is now defaulted or cleared in BeforeCreate/BeforeUpdate,
and is either inherited from the previous object (if nil or unchanged),
or set to the default strategy's family as necessary. The existing
family defaulting when cluster ip is provided remains in the api
section. We add additonal family defaulting at the time we allocate
the IP to ensure that IPFamily is a consequence of the ClusterIP
and prevent accidental reversion. This defaulting also ensures that
old clients that submit a nil IPFamily for non ClusterIP services
receive a default.
To properly handle validation, make the strategy and the validation code
path condition on which configuration options are passed to service
storage. Move validation and preparation logic inside the strategy where
it belongs. Service validation is now dependent on the configuration of
the server, and as such ValidateConditionService needs to know what the
allowed families are.
