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/configure.yml

@@ -15,7 +15,7 @@
     src: "etcd-{{ etcd_deployment_type }}.service.j2"
     dest: /etc/systemd/system/etcd.service
     backup: yes
-  when: ansible_service_mgr == "systemd"
+  when: ansible_service_mgr == "systemd" and is_etcd_master
   notify: restart etcd
 
 - name: Configure | Write etcd initd script
@@ -24,5 +24,21 @@
     dest: /etc/init.d/etcd
     owner: root
     mode: 0755
-  when: ansible_service_mgr in ["sysvinit","upstart"] and ansible_os_family == "Debian"
+  when: ansible_service_mgr in ["sysvinit","upstart"] and ansible_os_family == "Debian" and is_etcd_master
   notify: restart etcd
+
+- name: Configure | Copy etcd-proxy.service systemd file
+  template:
+    src: "etcd-proxy-{{ etcd_deployment_type }}.service.j2"
+    dest: /etc/systemd/system/etcd-proxy.service
+    backup: yes
+  when: ansible_service_mgr == "systemd" and is_etcd_proxy
+  notify: restart etcd-proxy
+- name: Configure | Write etcd-proxy initd script
+  template:
+    src: "deb-etcd-proxy-{{ etcd_deployment_type }}.initd.j2"
+    dest: /etc/init.d/etcd-proxy
+    owner: root
+    mode: 0755
+  when: ansible_service_mgr in ["sysvinit","upstart"] and ansible_os_family == "Debian" and is_etcd_proxy
+  notify: restart etcd-proxy