[ci] Fix kitchen tests & salt states

Changes:

 - added 'is defined' check to compute|controller.enable opts

 - added creation of an empty policy.json file for newton+ release
   to allow to manage rules. (policy.json for nova is removed
   in stable/ocata, defaults are taken from code)

 - any nova manage * commands wrapped into 'noservice' condition

 - fixed .kitchen.yaml to manage releases in properly way (before
   change, Liberty release always used)

   wrong ways:

   pillars:
     - top.sls
     - nova <-------- will be created just 'nova' file, not 'nova.sls'

   pillars:
     - top.sls
     - nova.sls: <--- does not overwrite anything (file already exists)
        nova:
          version: ocata

Change-Id: I8c51f65979071148e22fb72a5f04b78e83074043
diff --git a/tests/pillar/control_single.sls b/tests/pillar/control_single.sls
index ce33f8c..78eaa40 100644
--- a/tests/pillar/control_single.sls
+++ b/tests/pillar/control_single.sls
@@ -57,6 +57,6 @@
       - host: 127.0.0.1
         port: 11211
     policy:
-      context_is_admin: 'role:admin or role:administrator'
+      'context_is_admin': 'role:admin or role:administrator'
       'compute:create': 'rule:admin_or_owner'
       'compute:create:attach_network':