tasks: Set Restart option for systemd service file

In order to have a consistent systemd behavior across distributions, we
define the Restart condition for the galera service file. The 'on-abort'
option is currently the default in the upstream service file and it's
also the most conservative one so we chose that to be the default option
in the Ansible role as well. We also set a reasonably low RestartSec
value as well.

Change-Id: If442802f7aff4473cbb573ba1c123cfc46bde9b3

tasks/galera_post_install.yml

@@ -104,6 +104,7 @@
   with_items:
     - { src: "systemd.limits.conf.j2", dest: "limits.conf" }
     - { src: "systemd.timeout.conf.j2", dest: "timeout.conf" }
+    - { src: "systemd.restart.conf.j2", dest: "restart.conf" }
   when:
     - ansible_service_mgr == 'systemd'
   notify:

templates/systemd.restart.conf.j2

@@ -0,0 +1,9 @@
+# {{ ansible_managed }}
+
+[Service]
+# Define the condition under which the service will be restarted
+# on-abort is the most conservative one since that should capture unexpected
+# failures but also exclude failures due to bad configurations. This is
+# currently the upstream option as well
+Restart=on-abort
+RestartSec=5s