Enable the Ceph mgr prometheus module when needed

Author: MoteHue

etc/kayobe/cephadm.yml

@@ -87,7 +87,12 @@ cephadm_cluster_network: "{{ storage_mgmt_net_name | net_cidr }}"
 # post-deployment configuration, post commands run after the rest of the
 # post-deployment configuration.
 #cephadm_commands_pre:
+{% if kolla_enable_prometheus_ceph_mgr_exporter %}
+cephadm_commands_post:
+  - "mgr module enable prometheus"
+{% else %}
 #cephadm_commands_post:
+{% endif %}
 
 ###############################################################################
 # Kolla Ceph auto-configuration.