make systemd enable work for mon instance

Signed-off-by: Huamin Chen <hchen@redhat.com>

roles/ceph-mon/tasks/start_monitor.yml

@@ -46,6 +46,13 @@
     ansible_distribution != "Ubuntu" and
     not is_ceph_infernalis
 
+- name: enable systemd unit file for mon instance (for or after infernalis)
+  command: "ln -s /usr/lib/systemd/system/ceph-mon@.service /etc/systemd/system/multi-user.target.wants/ceph-mon@{{ ansible_hostname }}.service"
+  changed_when: false
+  when:
+    ansible_distribution != "Ubuntu" and
+    is_ceph_infernalis
+
 - name: start and add that the monitor service to the init sequence (for or after infernalis)
   service:
       name: ceph-mon@{{ ansible_hostname }}