Add etcd proxy support

* Enforce a etcd-proxy role to a k8s-cluster group members. This
provides an HA layout for all of the k8s cluster internal clients.
* Proxies to be run on each node in the group as a separate etcd
instances with a readwrite proxy mode and listen the given endpoint,
which is either the access_ip:2379 or the localhost:2379.
* A notion for the 'kube_etcd_multiaccess' is: ignore endpoints and
loadbalancers and use the etcd members IPs as a comma-separated
list. Otherwise, clients shall use the local endpoint provided by a
etcd-proxy instances on each etcd node. A Netwroking plugins always
use that access mode.
* Fix apiserver's etcd servers args to use the etcd_access_endpoint.
* Fix networking plugins flannel/calico to use the etcd_endpoint.
* Fix name env var for non masters to be set as well.
* Fix etcd_client_url was not used anywhere and other etcd_* facts
evaluation was duplicated in a few places.
* Define proxy modes only in the env file, if not a master. Del
an automatic proxy mode decisions for etcd nodes in init/unit scripts.
* Use Wants= instead of Requires= as "This is the recommended way to
hook start-up of one unit to the start-up of another unit"
* Make apiserver/calico Wants= etcd-proxy to keep it always up

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
Co-authored-by: Matthew Mosesohn <mmosesohn@mirantis.com>

roles/kubernetes/master/templates/manifests/kube-apiserver.manifest.j2

@@ -11,7 +11,7 @@ spec:
     - /hyperkube
     - apiserver
     - --advertise-address={{ ip | default(ansible_default_ipv4.address) }}
-    - --etcd-servers={% for srv in groups['etcd'] %}http://{{ hostvars[srv]['access_ip'] | default(hostvars[srv]['ip']|default(hostvars[srv]['ansible_default_ipv4']['address'])) }}:2379{% if not loop.last %},{% endif %}{% endfor %}
+    - --etcd-servers={{ etcd_access_endpoint }}
     - --admission-control=NamespaceLifecycle,NamespaceExists,LimitRanger,SecurityContextDeny,ServiceAccount,ResourceQuota
     - --service-cluster-ip-range={{ kube_service_addresses }}
     - --client-ca-file={{ kube_cert_dir }}/ca.pem