tasks: neutron_db_setup: Only create the DB from the first neutron server

The DB creation task should only be executed once and ideally from a
single neutron-server host otherwise it's possible to hit a race condition
where multiple neutron server hosts try to create the same DB at the same
time and only one will eventually succeed leading to task failures such
as the following one:

 TASK [os_neutron : Create DB for service] **************************************
 changed: [server2]
 fatal: [server1]: FAILED! => {...}

Change-Id: I803c90f78bb0bfcccd8bc4c0c76db0755b2ddf32

tasks/neutron_db_setup.yml

@@ -22,6 +22,7 @@
     state: "present"
   delegate_to: "{{ neutron_db_setup_host }}"
   no_log: True
+  when: "inventory_hostname == ((groups[neutron_services['neutron-server']['group']]| intersect(ansible_play_hosts)) | list)[0]"
 
 - name: Grant access to the DB for the service
   mysql_user:
@@ -38,6 +39,7 @@
     - "localhost"
     - "%"
   no_log: True
+  when: "inventory_hostname == ((groups[neutron_services['neutron-server']['group']]| intersect(ansible_play_hosts)) | list)[0]"
 
 - name: Perform a DB expand
   command: "{{ neutron_bin }}/neutron-db-manage upgrade --expand"