Define condition for the first play host one time

We use the same condition, which defines against what host some "service"
tasks should run against, several times. It's hard to keep it the same
across the role and ansible spending additional resources to evaluate
it each time, so it's simpler and better for the maintenance to set
a boolean variable which will say for all tasks, that we want to run
only against signle host, if they should run or not now.

Change-Id: I6247f86b26d1e0dac55fa863a19405ff171c82ff

tasks/ceilometer_post_install.yml

@@ -66,7 +66,7 @@
   when:
     - item.condition | default(True)
     - item.tmp_f
-  run_once: true
+    - _ceilometer_is_first_play_host
 
 - name: Copy common config
   config_template:

tasks/main.yml

@@ -99,13 +99,11 @@
         password: "{{ ceilometer_service_password }}"
         role: "{{ ceilometer_role_name }}"
   when:
-    - ceilometer_services['ceilometer-agent-notification']['group'] | intersect(group_names) | length > 0
-    - inventory_hostname == (groups[(ceilometer_services['ceilometer-agent-notification']['group'] | intersect(group_names))[0]] | intersect(ansible_play_hosts))[0]
+    - _ceilometer_is_first_play_host
   tags:
     - ceilometer-config
 
 - import_tasks: mq_setup.yml
-  run_once: yes
   vars:
     _oslomsg_rpc_setup_host: "{{ ceilometer_oslomsg_rpc_setup_host }}"
     _oslomsg_rpc_userid: "{{ ceilometer_oslomsg_rpc_userid }}"
@@ -117,11 +115,14 @@
     _oslomsg_notify_password: "{{ ceilometer_oslomsg_notify_password }}"
     _oslomsg_notify_vhost: "{{ ceilometer_oslomsg_notify_vhost }}"
     _oslomsg_notify_transport: "{{ ceilometer_oslomsg_notify_transport }}"
+  when:
+    - _ceilometer_is_first_play_host
   tags:
     - common-mq
     - ceilometer-config
 
 - import_tasks: ceilometer_db_setup.yml
+  when:
+    - _ceilometer_is_first_play_host
   tags:
-    - ceilometer-config
-  run_once: true
+    - ceilometer-config

vars/main.yml

@@ -21,6 +21,8 @@ ceilometer_loadbalancer_v2_meter_definitions_user_content: "{{ lookup('file', ce
 ceilometer_osprofiler_event_definitions_user_content: "{{ lookup('file', ceilometer_osprofiler_event_definitions_default_file_path, errors='ignore') }}"
 ceilometer_polling_user_content: "{{ lookup('file', ceilometer_polling_default_file_path, errors='ignore') }}"
 
+_ceilometer_is_first_play_host: "{{ (ceilometer_services['ceilometer-agent-notification']['group'] | intersect(group_names) | length > 0) and (inventory_hostname == groups[ceilometer_services['ceilometer-agent-notification']['group'] | intersect(group_names) | first] | intersect(ansible_play_hosts) | first) }}"
+
 _ceilometer_rootwrap_conf_overrides:
   DEFAULT:
     filters_path: "/etc/ceilometer/rootwrap.d,/usr/share/ceilometer/rootwrap"