Add automatic restart for memcached

This patch ensures that systemd will restart memcached in case of
failure or if the process is manually killed.

Closes-Bug: 1659954
Change-Id: I6782320bf429cde17dff00401e7f136cfc979cee
(cherry picked from commit 4ec27e6874)

tasks/memcached_config.yml

@@ -61,6 +61,14 @@
     - ansible_service_mgr == 'systemd'
   notify: Restart memcached
 
+- name: Add automatic restart on failure
+  template:
+    src: systemd-restart-on-failure.conf.j2
+    dest: "/etc/systemd/system/memcached.service.d/systemd-restart-on-failure.conf"
+  when:
+    - ansible_service_mgr == 'systemd'
+  notify: Restart memcached
+
 - name: Apply resource limits (systemd)
   template:
     src: "limits.conf.j2"

templates/systemd-restart-on-failure.conf.j2

@@ -0,0 +1,4 @@
+# {{ ansible_managed }}
+[Service]
+Restart=on-failure
+RestartSec=2