Add step to enable the supervisor service.

Ubuntu bug report: https://bugs.launchpad.net/ubuntu/+source/supervisor/+bug/1594740
Update nginx restart command to use systemctl too.

docs/topics/deploying.rst

@@ -196,8 +196,9 @@ Make the installation directory readable and writable by the webserver user::
 
 Restart the services::
 
-    /etc/init.d/nginx restart
-    /etc/init.d/supervisor restart
+    systemctl enable supervisor
+    systemctl restart supervisor
+    systemctl restart nginx
 
 Docker method
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