Evaluate cephfs pool variables

Otherwise pools with names 'cephfs_data' and 'cephfs_metadata'
are created.

roles/ceph-mon/tasks/create_mds_filesystems.yml

@@ -6,8 +6,8 @@
 - name: create filesystem pools
   command: "{{ docker_exec_cmd }} ceph --cluster {{ cluster }} osd pool create {{ item }} {{ osd_pool_default_pg_num }}"
   with_items:
-    - cephfs_data
-    - cephfs_metadata
+    - "{{ cephfs_data }}"
+    - "{{ cephfs_metadata }}"
   changed_when: false
 
 - name: check if ceph filesystem already exists