* Added configurable local apiserver proxy liveness probe

* Enable API LB healthcheck by default

* Fix template spacing and moved healthz location to nginx http section

* Fix healthcheck listen address to allow kubelet request healthcheck

* Remove hard dependence on facts for all nodes

* Update main.yaml

* Update main.yaml

* Leave all.yml to keep only optional vars
* Store groups' specific vars by existing group names
* Fix optional vars casted as mandatory (add default())
* Fix missing defaults for an optional IP var
* Relink group_vars for terraform to reflect changes

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>

the which port the local nginx proxy should listen on for HA
local balancer configurations.

This proxy should only be listening for local connections, not 0.0.0.0.

Fixes #868

Fixes #655.

This is a teporary solution for long-polling idle connections to
apiserver. It will make Nginx not cut them for the duration of expected
timeout. It will also make Nginx extremely slow in realizing that there
is some issue with connectivity to apiserver as well, so it might not be
perfect permanent solution.

Also adds all masters by hostname and localhost/127.0.0.1 to
apiserver SSL certificate.

Includes documentation update on how localhost loadbalancer works.