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/etcd/tasks/main.yml

@@ -8,7 +8,12 @@
 - name: Restart etcd if binary changed
   command: /bin/true
   notify: restart etcd
-  when: etcd_deployment_type == "host" and etcd_copy.stdout_lines
+  when: etcd_deployment_type == "host" and etcd_copy.stdout_lines and is_etcd_master
+
+- name: Restart etcd-proxy if binary changed
+  command: /bin/true
+  notify: restart etcd-proxy
+  when: etcd_deployment_type == "host" and etcd_copy.stdout_lines and is_etcd_proxy
 
 # Reload systemd before starting service
 - meta: flush_handlers
@@ -18,6 +23,14 @@
     name: etcd
     state: started
     enabled: yes
+  when: is_etcd_master
+
+- name: Ensure etcd-proxy is running
+  service:
+    name: etcd-proxy
+    state: started
+    enabled: yes
+  when: is_etcd_proxy
 
 # After etcd cluster is assembled, make sure that
 # initial state of the cluster is in `existing`