add unique filter to openstack pool names

could have scenario where different openstack components would
use the same pool, but the logic would create the same pool
more than once

add unique filter to account for this

roles/ceph-mon/tasks/openstack_config.yml

@@ -1,7 +1,7 @@
 ---
 - name: create openstack pool
   command: ceph --cluster {{ cluster }} osd pool create {{ item.name }} {{ item.pg_num }}
-  with_items: "{{ openstack_pools }}"
+  with_items: "{{ openstack_pools | unique }}"
   changed_when: false
   failed_when: false