Prevent cinder conf from copy nfs_shares to unrelated nodes

Prevent cinder conf from copy nfs_shares to all nodes instead of
just cinder-volume.

Change-Id: I4f94b6c0ca8b628c1babee7fff0b66fb5a8df257
Closes-Bug: #1713010

ansible/roles/cinder/tasks/config.yml

@@ -87,6 +87,8 @@
   template:
     src: "{{ item }}"
     dest: "{{ node_config_directory }}/cinder-volume/nfs_shares"
+  when:
+    - inventory_hostname in groups[cinder_services["cinder-volume"]["group"]]
   with_first_found:
     - files:
         - "{{ node_custom_config }}/nfs_shares.j2"