Add freezer-scheduler hosts into site.yml

freezer-scheduer container will run on freezer-scheduler hosts[0],
but it missing in site.yml, when freezer-api and freezer-scheduler
run on different hosts, it will failed.

[0]: https://github.com/openstack/kolla-ansible/blob/master/ansible/inventory/multinode#L376

Change-Id: I1bd36c7c57345ee63cd153df8bd0603badf0d8a2

ansible/site.yml

@@ -698,6 +698,7 @@
   gather_facts: false
   hosts:
     - freezer-api
+    - freezer-scheduler
   serial: '{{ kolla_serial|default("0") }}'
   roles:
     - { role: freezer,