Change the dpkg -l to dpkg-query -s

The dpkg -l python will give 0 as result, because the python has un
(not-installed)status on xenial, switch to dpkg-query will give the
right status code(1) if the package is not installed.

Change-Id: I7faf1d922bdf0673d5daeec6fb2538f1786cbcd1

playbooks/openstack-hosts-setup.yml

@@ -36,7 +36,7 @@
             exit $result;
           ;;
           ubuntu)
-            dpkg -l python
+            dpkg-query -s python $> /dev/null
             result=$?
 
             if [ $result -eq 1 ]; then
@@ -48,6 +48,7 @@
           ;;
         esac
       changed_when: "result.rc == 2"
+      failed_when: "{{ result.rc not in [0, 2] }}"
 
 - name: Basic host setup
   hosts: "{{ openstack_host_group|default('hosts') }}"