Pass tiller namespace down to helm task

installer/roles/kubernetes/tasks/main.yml

@@ -85,6 +85,7 @@
       --set postgresPassword={{ pg_password }} \
       --set postgresDatabase={{ pg_database }} \
       --set persistence.size={{ pg_volume_capacity|default('5')}}Gi \
+      --tiller-namespace={{ tiller_namespace | default('kube-system') }} \
       stable/postgresql
   when:
     - pg_hostname is not defined or pg_hostname == ''