Mask nova-placement-api service

The nova-placement-api works as apache site, and should not be started as
system service. Continuous restart of system service causes 100% cpu usage.

Change-Id: I9c262eb3d5f4d410f4d0cf06ba9eaea678931379
diff --git a/nova/controller.sls b/nova/controller.sls
index fd4df62..01d4e18 100644
--- a/nova/controller.sls
+++ b/nova/controller.sls
@@ -92,9 +92,16 @@
   - require:
     - cmd: nova_controller_syncdb
 
+nova_placement_service_mask:
+  file.symlink:
+   - name: /etc/systemd/system/nova-placement-api.service
+   - target: /dev/null
+
 nova_placement_package:
   pkg.installed:
   - name: nova-placement-api
+  - require:
+    - file: nova_placement_service_mask
 
 /etc/apache2/sites-available/nova-placement-api.conf:
   file.managed: